Reducing Antibiotics Treatment Duration for Ventilator-Associated Pneumonia
Phase: PHASE3
Conditions: Ventilator Associated Pneumonia, Pneumonia, Bacterial
Sponsor: University of Oxford

Protocol 
Study Title:  
REducinG Antibiotics tReatment Duration for 
Ventilator-Associated Pneumonia (REGARD-VAP) 
Brief Title: 
Defining Antibiotic Treatment Duration for Ventilator 
- Associated Lung Infection (REGARD_VAP) 
Protocol Number:  
BAC17008 
NCT number:  
 
NCT03382548 
OxTREC Ref: 
 
40-17  
Date and Version No: 
version. 5.1 dated 28 July 2021 
Chief Investigator:  
Ben Cooper, Professor 
Mahidol-Oxford Tropical Medicine Research Unit, 
Mahidol University and University of Oxford 
 
 
 
 
 
 
 
 

Protocol version 5.1 dated 28 July 2021 
 
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Study Title:  REducinG Antibiotics tReatment Duration for Ventilator-Associated Pneumonia (REGARD-
VAP) 
Protocol Number: BAC17008 
 
OxTREC Ref: 40-17 
 
Date and Version No: version. 5.1  dated  28 July 2021 
 
Chief Investigator: 
Ben Cooper, Professor  
Mahidol-Oxford Tropical Medicine Research Unit, Mahidol University 
and University of Oxford 
 
 
Investigators:  
 
Direk Limmathurotsakul, Associate Professor  
Mahidol-Oxford Tropical Medicine Research Unit, Mahidol University 
and University of Oxford 
  
Mo Yin,  
National University Health System, Singapore and University of Oxford 
 
Sponsor:  
 
University of Oxford  
Funder: 
The project will be partly funded by Medical Research Council/ 
Department for International Development (MRC/DfID).  (Grant Ref: 
MR/K006924/1) and Singapore National Medical Research Council 
(Grant Ref: CTGIIT18MAY-005). 
Chief Investigator Signature:  
 
 
Potential conflicts of interest: 
There are no conflicts of interest.  
 
Confidentiality Statement 
This document contains confidential information that must not be disclosed to anyone other than the 
authorised individuals from the University of Oxford, the Investigator Team and members of the Oxford 
Tropical Research Ethics Committee (OxTREC), unless authorised to do so. 
 
 

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TABLE OF CONTENTS 
1. 
SYNOPSIS 
4 
2. 
ABBREVIATIONS 
6 
3. 
BACKGROUND AND RATIONALE 
7 
4. 
OBJECTIVES AND OUTCOME MEASURES 
9 
5. 
STUDY DESIGN 
10 
6. 
PARTICIPANT IDENTIFICATION AND RECRUITMENT 
13 
6.1. 
Study Participants 
13 
6.2. 
Inclusion Criteria 
13 
6.3. 
Exclusion Criteria 
14 
7. 
STUDY PROCEDURES 
14 
7.1. 
Recruitment 
14 
7.2. 
Screening and Eligibility Assessment 
14 
7.3. 
Informed Consent 
14 
7.4. 
Randomisation, blinding and unblinding 
15 
7.5. 
Baseline Assessments 
16 
7.6. 
Subsequent Visits 
16 
7.7. 
Sample Handling 
16 
7.8. 
Discontinuation/Withdrawal of Participants from Study 
17 
7.9. 
Definition of End of Study 
17 
8. 
INTERVENTIONS / INVESTIGATIONS 
18 
9. 
SAFETY REPORTING 
19 
9.1. 
Definition of Serious Adverse Events 
19 
9.2. 
Reporting Procedures for Serious Adverse Events 
19 
10. 
STATISTICS AND ANALYSIS 
20 
10.1. 
Description of Statistical Methods for Primary and Secondary Outcomes 
20 
10.2. 
The Number of Participants 
21 
10.3. 
Analysis of microbiota and whole genome sequencing 
21 
11. 
DATA MANAGEMENT 
22 
11.1. 
Access to Data 
22 
11.2. 
Data Handling and Record Keeping 
22 
12. 
QUALITY CONTROL AND QUALITY ASSURANCE PROCEDURES 
22 
13. 
ETHICAL AND REGULATORY CONSIDERATIONS 
23 
13.1. 
Declaration of Helsinki 
23 

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13.2. 
Guidelines for Good Clinical Practice 
23 
13.3. 
Approvals 
23 
13.4. 
Participant Confidentiality 
23 
13.5. 
Expenses and Benefits 
24 
13.6. 
Reporting 
24 
14. 
FINANCE AND INSURANCE 
24 
14.1. 
Funding 
24 
14.2. 
Insurance 
24 
15. 
PUBLICATION POLICY 
24 
16. 
REFERENCES 
25 
17. 
APPENDIX A:  STUDY FLOW CHART 
28 
18. 
APPENDIX B:  SCHEDULE OF STUDY PROCEDURES 
30 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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1. SYNOPSIS 
Study Title 
REducinG Antibiotics tReatment Duration for Ventilator-Associated 
Pneumonia (REGARD-VAP) 
Protocol no.  
BAC17008 
Study Design 
Randomised, partially double-blind (blinding may be achieved up to 7 days) 
controlled trial to assess the non-inferiority, followed by superiority, of a 
short duration of antibiotics (up to 7 days) versus prolonged antibiotic 
therapy (as per physician preference) in adult patients with VAP  
Study Participants 
Adult patients (≥18 years old) who satisfy inclusion and exclusion criteria for 
VAP  
Planned Sample Size 
460 
Planned Study Period 
2018 January – 2022 October 
 
Objectives 
Outcome Measures 
Primary 
 
 
 
To demonstrate clinical non-
inferiority, followed by superiority, of 
a shorter antibiotic treatment 
duration compared to a longer 
duration in adult patients with VAP  
Difference in the proportion of 
participants with the composite 
endpoint of death and VAP 
recurrence rate within 60(±5) days 
of enrolment 
Secondary 
 
To define other clinical benefits of 
shorter antibiotic treatment duration 
compared to a longer duration in 
adult patients with VAP  
 
Ventilator-associated events, 
duration of mechanical ventilation, 
duration of hospitalisation, 
acquisition of multidrug resistant 
infection or colonisation during 
the hospitalisation, number of 
days of exposure to antibiotics 
during the hospitalisation, number 
and types of extrapulmonary 
infections during hospitalisation 
(determined from cultures taken 
from sterile sites) difference in the 
proportion of participants with 
primary outcome in subgroups of 
patients with VAP caused by 
Gram-negative non-fermenters 
and carbapenem-resistant bacilli 
To study the impact of various 
antibiotic regimen on the microbial 
community dynamics and diversity in 
the respiratory and intestinal tracts in 
individual patients in order to 
understand colonisation and 
transmission of MDROs, identify 
potentially protective components of 
the microbiome against MDROs  
Characteristics of the microbiota 
will be determined by comparing 
alpha and beta diversity metrics 
between the groups of patients, 
alterations in the repertoire of 
antibiotic resistant genes, shifts in 
microbiota functional and 
metabolic capacity 

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To study the impact of antibiotic 
utilisation on the ward-level multidrug 
resistant organism emergence and 
transmission dynamics  
 
Prospective audit of antibiotic 
utilisation of participating wards, 
colonising bacteria in respiratory 
and stool samples, antibiograms of 
infective and colonising bacteria, 
whole genome and resistance 
genes sequencing of multidrug 
resistant isolates, mathematical 
modelling using sequencing data 
to track the spread of pathogens 
between hosts allowing for 
unobserved infection times, 
multiple independent 
introductions of the pathogen, and 
within-host genetic diversity 
To construct predictive models with 
comprehensive clinical and molecular 
epidemiological data to produce 
setting-specific and evidence based 
antibiotic policies 
Statistical models and patient 
screening algorithms in both low-
to- middle and high income 
settings to predict outcomes 
including proportion of adequate 
empiric therapy, expected deaths 
 
To estimate the changes to total costs 
and health benefits measured by 
Quality Adjusted Life Years (QALY) 
from implementing into practice the 
shorter antibiotic treatment duration 
Resources and costs used for 
clinical implementation of a new 
policy; changes to costs arising 
from new policy as shown by 
length of stay on the ICU and the 
ward change; antibiotics use; 
other consumables; tests and 
diagnostics 
 
Risks of adverse events 
associated with change in duration 
of ICU stay, particularly other 
hospital-acquired infections (HAIs). 
Impact on mortality risk and health 
related QoL from shortening 
length of stays in ICU and reducing 
incidences of other HAIs 
 
 
 
 
 

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2. ABBREVIATIONS 
CI 
Chief Investigator 
CRF 
Case Report Form 
ICU 
 Intensive care units  
OxTREC 
Oxford Tropical Research Ethics Committee 
PI 
Principal Investigator 
VAP 
 Ventilator-Associated Pneumonia  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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3. BACKGROUND AND RATIONALE 
Hospitals and, in particular, intensive care units (ICUs) are epicenters for the emergence and dissemination 
of multidrug resistant (MDR) bacteria. ICUs have the most vulnerable patient population due to frequent 
use of invasive devices which break anatomical barriers, bypass host defences and distort normal 
protective microbiomes, because of high antimicrobial consumption. Consequently, the ICU population has 
one of the highest rates of nosocomial infections leading to a significant impact on healthcare costs, 
morbidity and survival [1]. With their controlled settings and well-defined patient populations, ICUs 
present an opportunity to conduct robust interventional and epidemiological studies on the effect of 
antimicrobial use on the emergence and spread of MDROs in individual patients as well as on the overall 
ecology in the ICU environment. Carefully conducted regional multi-centre trials in ICUs will provide 
important results that can potentially be extrapolated to larger clinical settings via epidemiological 
modelling to estimate the impact of the measures studied if these are well adopted for the whole Asian 
region. 
VAP is the most common nosocomial infection in patients in ICUs. As demonstrated in a cross-sectional 
prevalence survey in 1,417 ICUs worldwide, the prevalence of respiratory tract infection was 64% among 
all patients with nosocomial infections [2]. Estimates of all- cause mortality in patients with VAP range 
from 20-50% [3,4], and can be as high as 94% in low- to middle-income countries [5]. VAP prolongs the 
length of mechanical ventilation by 7.6-11.5 days and prolongs hospitalisation by 11.5 - 13.1 days 
compared with similar patients without VAP, and the excess cost associated with VAP has been estimated 
at USD$40,000 per patient in the United States [6,7]. Given its high prevalence and associated antibiotic 
usage, VAP is likely to be a key driver of antimicrobial resistance (AMR) in ICUs. 
Over the last few decades, we have continued to rely on the standard clinical, radiographic, and 
microbiological criteria with a low sensitivity and specificity of between 70 and 75% to diagnose VAP, 
respectively [8]. Identification of specific causative organisms is also difficult as the respiratory tract is non-
sterile. Concordance between tracheal non-quantitative cultures and cultures of lung tissue from open 
lung biopsy was found to be as low as 40% [9]. These factors result in over-diagnosis and over-treatment of 
organisms thought to be causing VAP with empirical combinations of broad-spectrum antibiotics. For those 
patients who are on culture-directed definitive antibiotics, duration of treatment remains controversial. 
There are two notable clinical trials from France that have suggested that a short course of 8 days has 
comparable clinical efficacy as a long duration of 15 days [10,11]. However, these studies could not 
confidently conclude that the finding can be applied to VAP caused by non-fermenting Gram-negative 
bacilli due to increased recurrence in such patients. Important potential biases also exist in those studies. 
For example: long-course therapy is favoured due to the differential time period during which recurrence 
was assessed, persistent colonisation could have been erroneously classified as recurrent infections, and 
the observed non-significant high rate of recurrence in those caused by non-fermenting Gram-negative 
bacilli could be a spurious finding due to subgroup over-analyses [10,11]. This severely limits the 
applicability of the current recommendation in Asia. This is because the majority of VAP in this region are 
caused by non-fermenting Gram-negative bacilli such as Pseudomonas aeruginosa and Acinetobacter 
baumannii [12-15]. The current median number of days of antibiotic treatment remains at 12-13 days in 
Thailand [16, 17].  Currently available studies also suffer from narrowly defined inclusion criteria that 
excluded culture-negative VAP. This limits generalisability of the findings to VAP caused by unknown 
organisms. Therefore, it is crucial to define whether a short duration of antimicrobial therapy for VAP 
would provide equivalent clinical outcome and yield lower emergence of MDRO in Asian settings.  

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Because of the uncertainty about the exact causative organisms, ICUs are likely to utilise a high proportion 
of inappropriate empirical broad-spectrum antibiotics [17], which might contribute to the indirect 
‘collateral damage’ of AMR emergence and dissemination to other patients. In Thailand, an alarming 95% 
of A. baumannii and 75% of P. aeruginosa isolates were recently found to be resistant to carbapenems, 
and 47% of K. pneumoniae isolates were ESBL-producing in VAP [18]. In Singapore, 91% of A. baumannii 
and 22% of all Gram-negative isolates collected during a 4-month period in 2010 were resistant to 
carbapenems in the “Comparative Activity of Carbapenem Testing” (COMPACT) study [19]. This 
emphasizes the importance of antimicrobial stewardship programmes (ASPs) which have shown to be 
capable of reducing broad-spectrum antibiotic consumption and potentially decreasing antibiotic 
resistance, particularly among Gram-negative pathogens [20-22]. However, current recommendations on 
ASP are based on very few conclusive studies as most ASP research was designed to evaluate cost-
effectiveness instead of clinical outcomes such as reducing selection of MDR pathogens, mortality, hospital 
length of stay, and readmission rates [23-25]. In addition, operational delivery of ASPs is often hindered by 
cost, lack of diagnostics and data collection facilities, poor physician participation and lack of cooperative 
strategies [26]. Low uptake of ASPs, especially in SEA [27], calls for more rigorous and methodologically 
sound evaluations of ASP interventions to initiate practice and policy changes. Mathematical models offer 
tremendous potential for assessing the effectiveness of ASPs by removing the limitations inherent in 
human experimentation, including potential health risks, study cohort size and duration [28]. To date, the 
potential of modelling in evaluating ASPs in control of antimicrobial resistance is largely untapped and 
much work remains to be done to leverage this potential. 
We aim to rationalise and reduce antibiotic consumption in ICUs and assess the benefit of this on both the 
individual patient and the overall cohort of ventilated patients. The specific aims are:  
i) to conduct a randomised controlled trial to assess the clinical efficacy of a short duration of 
antibiotics (up to 7 days) versus prolonged antibiotic therapy (physician preference) in adults patients 
with VAP ; 
ii) to study the changes in individuals’ microbiota and the impact on pathogen transmission dynamics 
and ward ecology with the use of various antibiotic regimens; and 
iii) to characterise current antibiotic utilisation in the ICU and develop locally optimised, setting-
specific empirical antibiotic policies. 
This study includes adult patients (≥18 years old) who satisfy our inclusion criteria for VAP after ≥ 48 hours 
of mechanical ventilation.  
 
Patient recruitment will be from:  
1) National University Hospital, Singapore  
2) Tan Tock Seng Hospital, Singapore  
3) Sunpasitthiprasong Hospital, Ubon Ratchathani, Thailand  
4) Srinagarind Hospital, Khon Kaen, Thailand  
5) Patan Academy of Health Science, Patan Hospital, Kathmandu, Nepal  
6) Civil Hospital, Kathmandu, Nepal  
7) Khon Kaen Hospital, Khon Kaen, Thailand 

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8) Cajuru University Hospital, Pontifical Catholic University of Paraná, Brazil 
 
The results of the study will be generalizable to adult ventilated patients from both low-to-middle and 
high-income countries, especially those with VAP caused by Gram-negative bacteria.  
4. OBJECTIVES AND OUTCOME MEASURES 
Objectives 
Outcome Measures  
 
Timepoint(s) of 
evaluation of this 
outcome measure 
(if applicable)  
Primary Objective 
To demonstrate clinical non-
inferiority, followed by superiority, 
of a shorter antibiotic treatment 
duration compared to a longer 
duration in adult patients with VAP  
Difference in the proportion of participants 
with the composite endpoint of death and 
VAP recurrence rate within 60(+5) days of 
enrolment 
All outcome 
measures will be 
assessed within day 
60(+5) of 
enrolment 
Secondary Objectives 
To define other clinical benefits of 
shorter antibiotic treatment 
duration compared to a longer 
duration in adult patients with VAP  
 
Ventilator-associated events, duration of 
mechanical ventilation, duration of 
hospitalisation, acquisition of multidrug 
resistant infection or colonisation during 
the hospitalisation, number of days of 
exposure to antibiotics during 
hospitalisation, number and types of 
extrapulmonary infections during 
hospitalisation (determined from cultures 
taken from sterile sites), difference in the 
proportion of participants with primary 
outcome in subgroups of patients with VAP 
caused by Gram-negative non-fermenters 
and carbapenem-resistant bacilli 
All outcome 
measures will be 
assessed within day 
60(+5) of 
enrolment 
 
To study the impact of various 
antibiotic regimen on the microbial 
community dynamics and diversity 
in the respiratory and intestinal 
tracts in individual patients in order 
to understand colonisation and 
transmission of MDROs, identify 
potentially protective components 
of the microbiome against MDROs 
Characteristics of the microbiota will be 
determined by comparing alpha and beta 
diversity metrics between the groups of 
patients, alterations in the repertoire of 
antibiotic resistant genes, shifts in 
microbiota functional and metabolic 
capacity 
Respiratory and 
stool samples will 
be collected from 
the study 
participants within 
24 hours of 
enrolment, weekly 
during 
hospitalisation, and 
at day 28 (+5) and 
60(+5) after 
enrolment 

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To study the impact of antibiotic 
utilisation on the ward-level 
multidrug resistant organism 
emergence and transmission 
dynamics 
Prospective audit of antibiotic utilisation of 
participating wards, colonising bacteria in 
respiratory and stool samples, 
antibiograms of infective and colonising 
bacteria, whole genome and resistance 
genes sequencing of multidrug resistant 
isolates, mathematical modelling using 
sequencing data to track the spread of 
pathogens between hosts allowing for 
unobserved infection times, multiple 
independent introductions of the 
pathogen, and within-host genetic 
diversity 
These will be 
measured 
throughout the 
duration of the 
study in 
participating wards 
To construct predictive models with 
comprehensive clinical and 
molecular epidemiological data to 
produce setting-specific and 
evidence based antibiotic policies 
Statistical models and patient screening 
algorithms in both low-to- middle and high 
income settings to predict outcomes 
including proportion of adequate empiric 
therapy, expected deaths 
N.A. 
To estimate the changes to total 
costs and health benefits measured 
by QALY from implementing into 
practice the shorter antibiotic 
treatment duration 
 
Resources and costs used for clinical 
implementation of a new policy; changes 
to costs arising from new policy as shown 
by length of stay on the ICU and the ward 
change; antibiotics use; other 
consumables; tests and diagnostics 
 
Risks of adverse events associated with 
change in duration of ICU stay, particularly 
other HAIs. Impact on mortality risk and 
health related quality of life from 
shortening length of stay in ICU and 
reducing incidences of other HAIs 
Data collected 
during the trial will 
be used and 
combined with 
other data sources 
from the study 
hospitals and 
published literature 
to predict costs and 
health outcomes 
for a time period 
that exceeds the 
trial duration 
5. STUDY DESIGN 
The study design is a randomised, partially double-blinded (blinding may be achieved up to 7 days) 
controlled trial to assess the efficacy of short vs. longer antibiotics course in adults with VAP . The trial has 
a stepwise noninferiority–superiority hypothesis, i.e., if non-inferiority of short duration, compared with 
long duration, is shown, statistical tests for superiority will be performed using closed testing methods 
without requiring adjustment of the significance level for multiple comparisons. 
Screening and inclusion criteria  
We will apply the US Centers for Disease Control and Prevention (CDC) National Healthcare Safety Network 
(NHSN) VAP diagnostic criteria on patients who have been mechanically ventilated for ≥48 hours as our 

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study subject inclusion criteria [29]. While we acknowledge that there is no “gold standard” diagnostic 
criteria to VAP and that clinical criteria correlate poorly with autopsy findings (previously determined to be 
69 % sensitivity and 75 % specificity [30]), the CDC NHSN diagnostic criteria is sensitive and practical for use 
in ICUs of various resources and settings. Only one episode of suspected VAP will be included for this 
study.  
We agree with the 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA) 
and the American Thoracic Society (ATS) guideline that the additional use of infection scores and other 
biomarkers including procalcitonin, c-reactive protein, and soluble triggering receptor expressed on 
myeloid cells-1 lack sensitivity and specificity and will not be included in our inclusion criteria [3].   
Microbiological culture results are not part of our inclusion criteria so that we are able to recruit patients 
who have suspected VAP but respiratory cultures are negative. Management strategies for this group of 
patients have not been defined by a randomised study. There are two observational studies that compared 
outcomes among those whose antibiotics were withheld on the basis of negative respiratory cultures to 
those whose antibiotics were continued [32, 33]. Patients whose antibiotics were discontinued did not 
have a higher mortality or rate of new respiratory infection compared to patients whose antibiotics were 
continued.  
Randomisation and Intervention  
Following screening and fulfilling the inclusion/exclusion criteria, the study subject will be recruited within 
72 hours. Antibiotic treatment course will be determined according to randomisation.  
Participants in the intervention (short duration) arm will receive antibiotics for up to 7 days. Antibiotics 
should be stopped from day 3 to 7 if respiratory cultures are negative and the patients fulfil a set of 
stringent clinical criteria signifying cardiopulmonary stability for 48 hours. If the respiratory cultures are 
positive, patients who fulfil the same set of clinical criteria should have their antibiotics stopped from day 5 
to 7 (see section 8. Interventions). Antibiotics administered via all routes i.e. intravenous, oral and 
nebulisation should be stopped.  Randomisation will be carried out when the participants fulfil the clinical 
stop criteria. The rationale for stopping antibiotics at the above time points is as follows:  
Group 1: Short Duration arm 
(a) Day 3  
Patients who have negative respiratory cultures should have their antibiotics stopped from day 3 
to 7 if the patient satisfies a set of criteria signifying clinical stability. As discussed above, though 
there are no randomised studies to support this, there are 2 observational studies [32, 33] showing 
that discontinuation of antibiotics in these cases did not result in a higher mortality or rate of new 
respiratory infections compared to those whose antibiotics were continued.  In addition, those 
whose antibiotics were withheld had a lower rate of total secondary infections by MDROs. One of 
these studies concluded that antibiotics could be safely discontinued in patients with negative 
respiratory cultures with no significant impact on mortality, despite persistence of signs and 
symptoms of pneumonia in 35% of these patients [32]. The above studies have led to the 
recommendation in the 2016 IDSA/ATS guideline that for patients with suspected VAP whose 
respiratory invasive culture results are below the diagnostic threshold for VAP, antibiotics should 
be withheld rather than continued [3].   

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(b) Day 5-7  
The 2016 IDSA/ATS VAP guideline recommends a 7-day course of antimicrobial therapy for the 
treatment of VAP [3]. However, 7-day course is empirical and durations shorter than 7 days have 
been studied in randomised trials. One of these studies by Singh et al [33] evaluated 3 days of 
empirical ciprofloxacin monotherapy for patients who satisfy a set of clinical criteria signifying low 
likelihood of active VAP at day 3 of treatment. Compared to those who received longer duration of 
antibiotics, there was no difference in mortality or ICU length of stay. Patients in the short duration 
group had less antibiotic resistance and fewer superinfections. Another randomised study by 
Micek et al [34], adopted an antibiotic discontinuation policy to shorten VAP treatment. Similarly 
there was no difference between the short (6.0 ± 4.9 days) and long duration treatment groups in 
terms of mortality and VAP recurrences. The majority of the causative pathogens in this study are 
Gram-negative bacteria including Pseudomonas and Acinetobacter, which are also the commonest 
VAP pathogens in Asia [34]. The above evidence supports the use of a set of clinical stability criteria 
to establish the duration of antibiotic treatment for VAP.  
The set of clinical stability criteria used in this study is adopted from Micek et al [34], and IDSA/ATS 
consensus guidelines on the management of community-acquired pneumonia in adults [35]. The 
community-acquired pneumonia guideline is used because a similar set of clinical stability criteria 
was not defined in the IDSA/ATS VAP guideline.  
Group 2: Long Duration arm  
Participants in the control (long duration) arm will receive standard care, which is antibiotic treatment for 
at least 8 days with the exact duration decided by the primary physician.  
Sample and data collection 
Respiratory samples (at least 1 set) will be collected from the participants within 24 hours of enrolment, if 
not yet collected by the managing physician, for microbiological cultures. Respiratory cultures will be 
collected either via the endotracheal tube (ETT) or bronchoalveolar lavage (BAL) as ordered by the primary 
physicians. Both non-invasive (ETT) and invasive (BAL) samples are acceptable methods for microbiological 
diagnosis of VAP.  No difference in mortality in the invasive versus non-invasive groups was shown in large 
randomised controlled studies including the Canadian Clinical Trials study [36], and subsequently a 
Cochrane meta-analysis [37] of 1,367 patients with VAP. Bacterial isolates grown from all other routine 
clinical cultures such as blood, cerebral spinal fluid, pus etc, will be retrieved from the microbiology 
laboratory and frozen and stored. These isolates will undergo whole genome sequencing to compare the 
within-host evolution of resistant organisms.  
For microbiome studies, 1 set of respiratory and stool samples will be collected within 24 hours and weekly 
during hospitalisation for DNA extraction and microbiome analysis.   
We will collect relevant clinical and microbiological data from the participants throughout their 
hospitalisation. Data collection will be done via review of medical records, microbiological culture results 
and drug administrative charts. 
Concurrently, we will collect prospective data on antibiotics utilisation, adaption and compliance of VAP 
prevention bundles and hand hygiene rates in the participating units. These audits will include patients 

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who are not study participants. These data are important as they are potential confounders to our 
outcome measures including mortality, VAP recurrence rate, duration of mechanical ventilation, 
acquisition of MDRO infection, and number and types of extrapulmonary infections during hospitalisation. 
Consents will not be required for these patients not directly participating in the study because these audits 
are standard procedures in hospitals.  
Follow-up visits  
The composite endpoint of death and VAP recurrence rate is assessed at 60(±5) days of enrolment done 
via an inpatient or outpatient follow-up visit. The time point of day 60(±5) is chosen, in contrast with day 
28 in previous studies, to avoid a bias in favouring long duration of treatment in assessment of VAP 
recurrences. A longer time point is deemed impractical and may contribute to high loss-to-follow-up rates 
especially for patients who reside in rural and remote areas.  
Two follow-up visits are scheduled at day 28(+5) and 60(+5). One set of respiratory and stool sample will 
be collected from all participants. The expected duration of participant participation is 60(±5) days from 
recruitment. Please see appendix B for schedule of study procedures.  
6. PARTICIPANT IDENTIFICATION AND RECRUITMENT 
6.1. Study Participants 
Adult patients (≥18 years old) in participating wards who have been on mechanical ventilation for more 
than 48 hours.  
6.2. 
Inclusion Criteria 
a. 
Patients 18 years and older 
b. 
Invasive mechanical ventilation ≥ 48 hours 
c. 
Satisfy the US Centers for Disease Control and Prevention National Healthcare Safety Network VAP 
diagnostic criteria [29] 
o 
At least one of the following:  
1. temperature > 38 °C  
2. white blood cell count ≥ 12,000 cells/mm3 or ≤ 4,000 cells/mm3 
3. altered mental status with no other causes in > 70 year-olds; AND  
o 
Two or more chest imaging tests demonstrating at least one of the following:  
1. new and progressive OR progressive and persistent infiltrate 
2. new and persistent OR progressive and persistent consolidation 
3. new and persistent OR progressive and persistent cavitation, AND 
o 
At least two of the following:  
1. new onset of purulent sputum, or change in character of sputum, or increased 
respiratory secretions, or increased in suctioning requirements 
2. new onset or worsening tachypnea or dyspnea 
3. rales or bronchial breath sounds 
4. worsening gas exchange defined by oxygen desaturations (e.g., PaO2/FiO2 <240), 
increased oxygen requirements or increased ventilation demand  
5.  

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6.3. 
Exclusion Criteria 
a. Poor likelihood of survival as defined by a Sepsis-related Organ Failure Assessment score (SOFA score) 
of >11 points [38]  
b. Immunocompromised patients (HIV with CD4 <200 cells/mm3, corticosteroids> 0.5 mg/kg per day for > 
30 days, received chemotherapy in the past 3 months, solid organ or hematopoietic cell transplant) 
c. Patients receiving antibiotic therapy for any other defined extra-pulmonary infections that warrant a 
duration of antibiotics longer than 7 days or complications of pneumonia such as lung abscess or 
empyema that warrant a duration of antibiotics longer than 7 days (excluding anti-tuberculosis 
treatment, antifungal medications, antibiotics meant for chronic suppression of chronic infections or 
chronic obstructive lung disease)  
d. Patients who have been treated for VAP for more than 7 days from screening  
e. Vulnerable population including prisoners and refugees  
7. STUDY PROCEDURES 
7.1. 
Recruitment 
Relevant sub-specialists such as general medicine, respiratory, infectious disease, intensive care and 
anaesthesia physicians, nurses and pharmacists involved in the care of ventilated patients from all 
participating sites will be briefed on the study protocol in advance. With their support, a site PI will be 
nominated to head the study.  
The study team will do screening for potential subjects. Potential subjects are identified according to the 
eligibility criteria stated above. When a potential subject is identified, our study team will approach the 
primary physician for his/ her permission for the study team to speak to the patient or patient’s legal 
representative or patient’s next-of-kin (NOK) for consent. Patient’s legal representative or NOK may be 
then contacted via phone call or in person. Discussion and explanation of the study procedures and signing 
of the consent will be done face-to-face.  
7.2. 
Screening and Eligibility Assessment 
Screening will be done on all mechanically ventilated patients in the respective study sites according to the 
eligibility criteria stated above. Participants should be recruited into the study as soon as possible after 
screening. A maximum of 72 hours is allowed between screening (fulfilment of the inclusion/exclusion 
criteria) and recruitment.   
7.3. 
Informed Consent 
Participants’ legal representatives or NOKs will be asked to represent the participants if the participants 
are sedated and do not have the capacity to make informed decision to participate in the study. The 
participants, their legal representatives or NOKs must personally sign and date the latest approved version 
of the Informed Consent form before any study specific procedures are performed. 
Written and verbal versions of the Participant Information and Informed Consent will be presented to the 
participants, their legal representatives or NOKs detailing no less than: the exact nature of the study; what 
it will involve for the participant; the implications and constraints of the protocol; the known side effects 
and any risks involved in taking part. It will be clearly stated that the participant, his/her legal 

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representative or NOK (on behalf of the participant) is free to withdraw from the study at any time for any 
reason without prejudice to future care, and with no obligation to give the reason for withdrawal. 
The participants, his/her legal representatives or NOKs will be allowed sufficient time to consider the 
information, and the opportunity to question the Investigator or other independent parties to decide 
whether they will participate in the study. Written Informed Consent will then be obtained by means of 
participants’, their legal representatives’ or NOKs’ dated signatures and dated signature of the person who 
presented and obtained the Informed Consent. The person who obtained the consent must be suitably 
qualified and experienced, and have been authorised to do so by the Investigator. A copy of the signed 
Informed Consent will be given to the participants, their legal representatives or NOKs. The original signed 
form will be retained at the study site. 
When the participants are deemed to have decision-making capacity by the primary physicians, he/she will 
be re-consented with the same procedures as above.  
The concurrent prospective data on clinical cultures, antibiotics utilisation, adaption and compliance of 
VAP prevention bundles and hand hygiene rates will involve all participating wards throughout the period 
of the study. All patients admitted to these units will be included as part of this audit and consents will not 
be taken for this purpose. All information collected as part of the audit will be anonymised to ensure 
patient confidentiality.  
As the time window for consent taking is limited, and visitation restrictions during the COVID-19 pandemic, 
oral consent may be used for participant enrolled temporarily. When oral consents are taken, the study 
team will be recording the information in the “research record for oral consent” (version 1.0, 8th July 2021). 
Written consent will be obtained as soon as direct contact with participant or participant’s family is 
possible according to the local hospital policies.  
7.4. 
Randomisation, blinding and unblinding 
Randomisation will be done via stratified block randomisation by the study sites to ensure participants 
with similar characteristics such as gender and age are distributed equally in the intervention and control 
groups. Randomisation will be done with a computer programme with a seed to allow reproducibility. 
Randomisation will be done with a 1:1 ratio. To prevent predictability of the random sequence, generation 
of the randomisation sequence is performed by an independent statistician and details of the 
randomisation generation is unavailable to all investigators. Randomisation will be allocated using 
sequentially numbered opaque envelopes. Fitness criteria for randomisation (section 8) must be met prior 
to randomisation.  
Patients will be blinded to the study, as they will not be informed of the treatment duration and likely to 
be sedated and unaware of the treatment regimens. Investigators will be blinded during the assessment of 
the participants for clinical stability based on the above-described criteria to minimise observer bias. Once 
conditions for stopping antibiotics are satisfied, the investigator will be unblinded and contact the primary 
physicians to stop antibiotics. The physicians will remain blinded until they are informed that the 
participant is suitable to stop antibiotics. Independent assessors, who are assigned to determine 
pneumonia recurrences, will be blinded from the randomisation arms. This will be achieved by blinding all 
study details, including randomisation arms, for participants with potential recurrences from these 
independent assessors.  

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7.5. 
Baseline Assessments 
At recruitment, participants’ demographics, medical history, antibiotics administration record, chest X-ray 
or other imaging findings, biochemical, microbiological and haematological results and clinical parameters 
will be collected. These are routine investigations ordered by the clinical teams taking care of the patients. 
Stool samples and upper and lower respiratory tract samples will be collected if they have not already 
been collected in the 24 hours prior to recruitment.  
7.6. 
Subsequent Visits  
Clinical information will be collected during participant’s hospitalisation. Two follow-ups will be done on 
day 28(+5) and 60(±5) after recruitment. During these visits, similar clinical information will be collected (if 
available) via hospital record review. Repeat respiratory and stool sample will also be collected. In the 
event that the participants are not able to attend the follow-ups in person, a telephone interview can be 
done in place of a physical visit.  
7.7. 
Sample Handling 
Respiratory cultures will be collected with the usual volume of 5-10ml per sample. Respiratory cultures 
may be collected via ETT, BAL or any other methods that the primary physician and local microbiology 
laboratories routinely use. Stool culture will be collected following defecation with the usual volume of 10-
50g per sample. Stool samples are collected at recruitment, weekly during hospitalisation and day 
28/60(±5) after enrolment.  
Microbiology cultures will be processed and reported in the local laboratories, which are expected to have 
standing quality control measures. Isolates, once identified, will be preserved, frozen and transported to 
an Oxford or Singapore study laboratory for genomic studies. These genomic results should concur with 
the initial microbiology laboratories’ identification of the isolates.  
a) 
Respiratory cultures  
All samples will be cultured and identified via standard microbiological methods. Susceptibility studies 
will be performed using EUCAST or CLSI agar method and breakpoints. Culture results with 
antibiogram are usually available within 48 to 72 hours after sample collection. 
 
Pathogens causing VAP and colonising MDROs will be processed for DNA extraction and undergo 
whole genome sequencing. These sequencing data will be used to track the spread of pathogens 
between hosts allowing for unobserved infection times, multiple independent introductions of the 
pathogen, and within-host genetic diversity.  
 
These isolates will be de-identified and stored for up to 15 years for use in future ethically approved 
studies. We will seek permission from the participants to store their samples and include this in the 
informed consents.  
 
b) 
Respiratory and stool samples  
For microbiome analysis, respiratory and stool samples will be processed for DNA extraction. Shotgun 
metagenomics approach will be used to characterise microbial community dynamics in the respiratory 
and intestinal tract. The characteristics of the microbiota will be determined by comparing alpha and 

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beta diversity metrics between the groups of patients to explore the short- and long- term impact of 
the various durations of antibiotics in individual patients. The data will also be used to assess if 
alterations in the repertoire of antibiotic resistant genes can be detected, and to study shifts in 
functional and metabolic capacity during the time course with a view to getting mechanistic insights 
into potentially protective components of the microbiome. 
 
These isolates will be de-identified and stored for up to 15 years for use in future ethically approved 
studies. We will seek permission from the participants to store their samples and include this in the 
informed consents.  
c)    Bacterial isolates from other routine clinical cultures such as blood, cerebral spinal fluid, pus etc 
All bacterial isolates including MDR Acinetobacter spp, Pseudomonas spp, Enterobacteriaceae, 
Staphylococcus aureus and Enterococcus spp, grown from other routine clinical cultures will be de-
identified and stored for up to 15 years for use in future ethically approved studies. In the current 
study, these isolates will undergo whole genome sequencing to compare the within-host evolution of 
resistant organisms. We will seek permission from the participants to store their samples for up to 15 
years in the informed consents.  
7.8. 
Discontinuation/Withdrawal of Participants from Study 
 
Each participant or NOK has the right to withdraw from the study at any time. The reason for withdrawal 
will be recorded in the Case Report Form. Withdrawal from the study will not result in exclusion of the 
data for that participant from analysis. 
In addition, the Investigator may discontinue a participant from the study at any time if the Investigator 
considers it necessary for any reason including but not limited to: 
● Ineligibility (either arising during the study or retrospectively having been overlooked at screening) 
● Significant protocol deviation 
● Significant non-compliance with treatment regimen or study requirements 
● Loss to follow up 
● Failure to meet fitness criteria by day 7  
 
We will compare baseline characteristics between patients who had protocol violations or who were 
unavailable for follow-up with those who did not. Follow-ups and data collection listed on the standard CRF 
for discontinued participants, including those who fail to be randomised, will be carried out within day 60(±5) 
of enrolment.  
 
Discontinued subject can be rescreened (under a new number). If the subject is rescreened, a new subject 
number will be allocated. The above patients will not be followed up once withdrawn or discontinued, and 
replaced to achieve the calculated sample size.  
7.9. 
Definition of End of Study 
The end of study is the date of the last follow-up visit of the last participant. 

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8. INTERVENTIONS / INVESTIGATIONS  
Antibiotic treatment for VAP will be tailored to the susceptibility of the pathogen(s) and in accordance to 
the 2016 IDSA/ATS VAP guideline [3]. Primary physicians are encouraged to convert initial empirical 
regimen to narrow- spectrum therapy based on culture results. In culture-negative cases, empirical 
antibiotic choice should be made depending on local antibiogram. The study team will not intervene on the 
antibiotics choices as this is beyond the objectives of the study.  
Number of days of antibiotics is calculated from the first day of appropriate coverage according to the 
susceptibility of at least 1 of the pathogen(s) recovered from respiratory cultures taken within 48h of 
screening or VAP symptom onset.  
For those participants randomised to the intervention (short duration) arm, site investigators should assess 
the patients daily. Antibiotics should be stopped at  
a) 
day 3 to 7, if all respiratory cultures during the same episode of VAP are negative, given that the 
criteria below are satisfied,  
b) 
day 5 to 7, if any of the respiratory cultures are positive is positive attributable to the current 
episode of VAP, given that the fitness criteria below are satisfied, 
a. body temperature was ≤ 38.3°C  (core body temperature measured orally or rectally) or 38.0°C 
(axillary)  for 48 hours, and 
b. hemodynamic instability (systolic blood pressure ≥ 90 mm Hg without inotropic support or no 
requirement of inotropic support to maintain systolic blood pressure above 90 mm Hg). 
In the short duration arm, all antibiotics should be withdrawn by day 7 (short duration) according to the 
randomisation assignment, except those participants with treatment failure in the case of persistent VAP 
or a new-onset infection of a different source prior to the last day of assigned duration of antibiotics. 
Persistent VAP or treatment failure is defined as the lack of improvement of hemodynamic stability or 
ventilation requirements without an alternative cause other than the same episode of VAP. These patients 
will be continued to be monitored for the above-described “fitness criteria” and antibiotics should be 
stopped when they eventually meet the criteria. Recurrent VAP is defined as an additional episode of VAP 
satisfying the CDC clinical and radiological criteria of VAP [29] following commencement of the primary 
VAP treatment within 60(+5) days of enrolment. Opinion from 2 respiratory experts blinded to the 
randomisation will be sought to diagnose persistence and recurrences. Patients who are diagnosed with an 
alternative source of infection or a complication from VAP such as lung abscess or empyema that warrant a 
duration of antibiotics longer than 7 days prior to the last day of assigned duration of antibiotics are not 
considered treatment failures. These patients will not meet fitness criteria for randomisation and be 
discontinued from the study and subsequent analysis (see section 7.8). In cases where patients 
randomised to short duration and satisfy the above-described “stop criteria” but did not have their 
antibiotics stopped by day 7, they are considered protocol deviations. They will be analysed with intention 
to treat analysis.  
Duration of antibiotics in control group will be at least 8 days with the exact duration decided by the 
managing physicians.  

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Adverse events will be recorded throughout the study period, including C. difficile infection, acute kidney 
injury, hepatitis, drug allergies, haematological and other complications. 
9. SAFETY REPORTING  
Participants in the shorter treatment duration arm may experience an increase in incidence of VAP relapse. 
Participating in the study will not delay the participants from receiving antibiotic treatment for recurrent 
VAPs. Decision to treat these participants for VAP recurrence will be made by the primary physicians.  
For outcome measurement purposes, opinion from 2 respiratory experts blinded to the randomisation will 
be sought to diagnose recurrences according to the above-described clinical and radiological criteria of 
VAP. Interim analysis will be done to ensure that participants in the shorter treatment duration arm are 
not experiencing a significant increase in incidence of ventilator-associated pneumonia relapse. 
9.1. 
Definition of Serious Adverse Events 
A serious adverse event is any untoward medical occurrence that: 
● results in death 
● is life-threatening 
● requires inpatient hospitalisation or prolongation of existing hospitalisation 
● results in persistent or significant disability/incapacity 
 
Other ‘important medical events’ may also be considered serious if they jeopardise the participant or 
require an intervention to prevent one of the above consequences. 
NOTE: The term "life-threatening" in the definition of "serious" refers to an event in which the participant 
was at risk of death at the time of the event; it does not refer to an event which hypothetically might have 
caused death if it were more severe. 
9.2. 
Reporting Procedures for Serious Adverse Events 
Given that VAP in ICU cohorts is associated with high mortality of 13.6–42.8% [41] and high recurrence rate 
previously shown in Southeast Asia, we would expect 55%-60% of our estimated sample size of 460 
patients to fulfil the above definition of SAE. This constitutes up to 276 (138 in each arm) participants that 
would require SAE reporting.  
As these events are very frequent and expected outcomes from ICU cohorts of patients, local Investigators 
will report mortalities and VAP recurrences that were ‘definitely related’ (definitely resulted from 
shortening antibiotic therapy duration), ‘probably related’ (some evidence that the event was resulted 
from shortening antibiotic therapy duration), ‘possibly related’ (little evidence that the event was resulted 
from shortening antibiotic therapy duration), and ‘not related’ (no evidence that the event was resulted 
from shortening antibiotic therapy duration) to CI on a monthly basis in the form of collated SAE reports. CI 
will, in turn, present these collated SAE reports to a nominated member of Data and Safety Monitoring 
Committee (DSMC) on a monthly basis. 

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Local investigator will present these SAE to the relevant local authorities according to local reporting 
requirements and timelines.  
To address the main risk of our study, which is that the participants in the intervention arm (short 
duration) may have higher recurrence and mortality rates, we have planned for four interim analysis for 
safety monitoring by the Data and Safety Monitoring Committee (DSMC).   
10. STATISTICS AND ANALYSIS 
10.1. 
Description of Statistical Methods for Primary and Secondary Outcomes 
Descriptive statistics will include frequency tables for categorical data, means (SDs), or medians 
(interquartile ranges) depending on the distribution of the data. Categorical variables will be compared 
with χ2 and Fisher exact tests as appropriate and continuous variables with unpaired, 2-tailed t tests or 
nonparametric Wilcoxon rank sum tests as appropriate.  
The primary and secondary outcomes of the study populations will be analyzed using both unadjusted and 
adjusted methods in both the per-protocol and intention-to-treat populations. Adjustment will be done 
with inverse probability weighting, using baseline patient characteristics (study site, age, gender, 
comorbidities, residence prior to admission, type of ICU admitted to, SOFA score, VAP infection with CRE, 
maximum heart rate and minimum mean arterial blood pressure on randomisation day, duration of 
intubation prior to developing VAP, reason for intubation, number of days from first respiratory symptom 
onset to first day of appropriate antibiotics) as independent variables.  
Subgroup analysis will be performed using the primary outcome as the dependent variable amongst 
patients with VAP caused by Gram-negative non-fermenters and carbapenem-resistant bacilli. VAPs caused 
by Gram-negative non-fermenters have been previously shown to be associated increased recurrence 
[10,11]. VAPs caused by carbapenem-resistant bacilli have no standardised treatment. This will be 
exploratory as the sample sizes for each of this groups will not reach adequate power.  
This is a non-inferiority trial with a hierarchical noninferiority–superiority hypothesis. The first analysis to 
be conducted will be for determination of non-inferiority. Only if non-inferiority is established by this 
primary analysis, a second analysis for superiority will be conducted using closed testing methods without 
requiring adjustment of the significance level for multiple comparisons. [39] The trial estimates for the 
primary outcome will be calculated with the absolute risk difference (proportion of participants with the 
primary outcome in the short arm minus that in the long arm). Hence, non-inferiority will be concluded if 
the upper boundaries of the one-sided 95% confidence intervals from both unadjusted and adjusted 
analyses are below the non-inferiority margin. The purpose of using both adjusted analyses on the 
intention-to-treat and per-protocol populations to determine non-inferiority is to minimise the inflation of 
type 1 error associated with non-adherence in non-inferiority trials. [40] Superiority will be declared if the 
entire confidence intervals for all the trial estimates are above zero. 
10.2. Definitions of study populations  
Intention-to-treat: The intention-to-treat population includes all study participants who have been 
randomised during the conduct of the study  

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Per-protocol: The per-protocol population includes all study participants who fulfill eligibility criteria 
specified in the inclusion/exclusion criteria (section 6.2 and 6.3), fitness criteria for randomisation (section 
8) and received 7 days or less of appropriate antibiotics in the short arm, and 8 days or more of 
appropriate antibiotics in the long arm. 
10.3. Interim analyses 
Four interim analyses will be performed on the primary endpoint whenever 25% of patients has been 
randomised and have completed the 60 (+5) days follow-up. The interim analyses will be performed by a 
trial statistician in coordination with the study team. The statistician will report to the independent data 
and Data and Safety Monitoring Committee (DSMC). The DSMC will have unblinded access to all data and 
will discuss the results of the interim-analysis during a DSMC meeting. A trial steering committee will also 
be constituted and will decide on the continuation of the trial and will report to the central ethics 
committee. The trial will be terminated if superiority of either short or long treatment durations is shown. 
We will use the group sequential design adopting the boundaries proposed by Fleming- Harrington- 
O’Brien (R=0.8) [41] to terminate the trial prematurely once the Z value exceeds the defined boundaries 
for superiority. 
10.2. 
The Number of Participants 
The study is designed to demonstrate the non-inferiority, followed by superiority, on the composite 
endpoint of mortality and recurrence at 60(±5) days of the short duration versus the long duration of 
antibiotic treatment for VAP. A meta-analysis showed that mortality attributable to VAP ranges from 13.6–
42.8% in Southeast Asia [42]. Considering that our primary outcome is a composite binary outcome of 
mortality and recurrence of VAP, we estimate this to be 55%. We derived an absolute non-inferiority 
margin of 12% with the fixed-margin method, preserving at least 50% of the efficacy of standard treatment 
in VAP. Using a group sequential design adopting the boundaries proposed by Fleming- Harrington- O’Brien 
(R=0.8) [40], a maximum of 412 patients will be required to achieve a power of 80% to conclude non-
inferiority between the two groups with an one-sided α risk of 5%. As we anticipate a loss to follow-up of 
up to 10%, we plan to enrol a maximum of 460 patients.  
10.3. 
Analysis of microbiota and whole genome sequencing  
Patients will be stratified into groups according to types and duration of antibiotic exposure. Shotgun 
metagenomics approach can be used to characterise microbial community dynamics in the respiratory and 
intestinal tract. The characteristics of the microbiota will be determined by comparing alpha and beta 
diversity metrics between the groups of patients and healthy volunteers to explore the short- and long- 
term impact of the various durations of antibiotics in individual patients. The data will also be used to 
assess if alterations in the repertoire of antibiotic resistant genes can be detected, and to study shifts in 
functional and metabolic capacity during the time course with a view to getting mechanistic insights into 
potentially protective components of the microbiome. 
10.4. Health economics modelling 
To assess the implementation cost, we will develop a logic model to describe the experience at each site to 
specify ‘inputs’, ‘activities’, ‘outputs’ and ‘outcomes’ arising from a policy of shortening duration 
of treatments. This will be developed with the site teams and managed by the research team 

Protocol version 5.1 dated 28 July 2021 
 
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for consistency in language and definitions. This exercise will provide an opportunity to identify the 
incremental resources required for the new policy. We expect most of the extra costs to be staff time, but 
there might be some other consumable or equipment costs. We will use qualitative methods to elicit 
information from local administrators and health services leaders. 
To assess the changes to costs arising directly from the new policy, we will use the trial data on lengths of 
stay, use of antibiotics, use of other consumables; and, tests and diagnostics. Unit costs will be sought from 
local administrators or shadow prices imputed where necessary. Data on adverse events associated with 
ICU stay will be assessed and augmented with information from the literature about how any unobserved 
adverse events change with ICU duration in similar populations. The costs of these events measured by 
excess length of stay will also be harvested from the literature; as will estimates of changes to risk of death 
and health related quality of life, measured by preference-based utility tools. 
The data we assemble will be organised in a decision tree or state-based model to capture chance events 
or frequently recurring events. For the economic modelling, the parameters that describe costs, health 
outcomes and probabilities will be fitted to prior uncertain distribution and simulation studies completed 
to propagate forward uncertainties to joint posterior distributions of change to costs and health benefits. 
Results will be presented as incremental cost-effectiveness ratios and rearranged as a net monetary 
benefits framework to show the probability that adoption of the novel model of care is cost-effective. 
Plausible thresholds for valuing health benefits will be used for each country. A probability that adoption is 
cost-effective that exceed 50% means a rational and risk neutral decision maker will adopt. Not adopting in 
this situation has a lower chance of being the best decision. The perspective of the health service will be 
adopted for this evaluation and good practice guidelines for reporting cost-effectiveness will be met. 
11. DATA MANAGEMENT 
11.1. 
Access to Data 
Direct access will be granted to authorised representatives from the University of Oxford and any host 
institution for monitoring and/or audit of the study to ensure compliance with regulations. 
11.2. 
Data Handling and Record Keeping 
All study data will be entered on MACRO, the Clinical Data Management System. The study database will 
be developed according to the approved Case Report Forms (CRFs). As for documents that contain patient 
identifiers, only the site PIs will have access to these documents.  
The MORU Data Management Standard Operating Procedures will be followed in the study. After the study 
is closed, the study documents will be kept in the accessible storage on request for 15 years. The final 
dataset will be archived in the data repository after the publication.  
12. QUALITY CONTROL AND QUALITY ASSURANCE PROCEDURES 
The study will be conducted in accordance with relevant regulations and standard operating 
procedures. 

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12.1 Study monitoring  
An appointed study monitor from the MORU clinical trial support group and a project coordinator will 
regularly visit the study sites for quality control. All study sites will be assessed prior to initiation of the 
study for capacity to conduct the randomised controlled trial, during the study and upon completion to 
ensure data quality. After site initiation, monitoring visits will perform monitoring on informed consent 
forms, CRF for completeness and accuracy of data and sample storage. There will be a minimum of three 
monitoring visits per study site: after 3-5 participants enrolled, after 50% of the target sample size enrolled 
for a particular site and upon study completion. Monitoring reports will be made available to the study 
sites and investigators after each visit. 
12.2 Strategies to improve adherence  
Regular meetings with the study sites will be carried out to ensure buy-in from the physicians and 
healthcare providers. Their feedback will be sought throughout the study, and improvements will be made 
in the study procedures to maintain ongoing support from the local ICUs. The study team will contact the 
primary physicians prior to enrolment and randomisation to ensure their adherence to allocated 
interventions.  
13. ETHICAL AND REGULATORY CONSIDERATIONS 
13.1. 
Declaration of Helsinki 
The CI will ensure that this study is conducted in accordance with the principles of the Declaration of 
Helsinki.  
13.2. 
Guidelines for Good Clinical Practice 
The CI will ensure that this study is conducted in accordance with relevant regulations and with Good 
Clinical Practice. 
13.3. 
Approvals 
The protocol, participant information sheet and informed consent form will be submitted to OxTREC and 
local ethics committees for written approval. 
The Investigator will submit and, where necessary, obtain approval from the above parties for all 
amendments to the original approved documents. 
13.4. 
Participant Confidentiality 
The study staff will ensure that the participants’ anonymity is maintained.  The participants will be 
identified only by a participant ID number on all study documents and any electronic database, with the 
exception of the CRF, where participant initials will be added.  All documents will be stored securely and 
only accessible by study staff and authorised personnel. The study will comply with the Data Protection 
Act, which requires data to be anonymised as soon as it is practical to do so. 

Protocol version 5.1 dated 28 July 2021 
 
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13.5. 
Expenses and Benefits 
The study team will reimburse reasonable travel expenses for any visits additional to normal care. 
13.6. 
Reporting 
The CI shall submit an Annual Progress Report to OxTREC and local ethics committees on the anniversary 
of the date of approval of the study. In addition, the CI shall submit an End of Study Report to OxTREC and 
local ethics committees. 
14. FINANCE AND INSURANCE 
14.1. 
Funding 
The project will be partly funded by Medical Research Council/ Department for International Development 
(MRC/DfID) (Grant Ref: MR/K006924/1) and Singapore National Medical Research Council (Grant Ref: 
CTGIIT18MAY-005). 
14.2. 
Insurance 
Specialist insurance policy is in place, which would operate in the event of any participant suffering harm 
as a result of their involvement in the research (Newline Underwriting Management Ltd, at Lloyd’s of 
London).   
15. PUBLICATION POLICY 
The CI will coordinate writing and reviewing of drafts of the manuscripts, abstracts, and any other 
publications arising from the study. Authorship will be determined in accordance with the ICMJE guidelines 
and other contributors will be acknowledged. 
 
 
 
 
 
 
 
 
 
 
 

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16. REFERENCES 
1. Brusselaers N, Vogelaers D, Blot S. The rising problem of antimicrobial resistance in the intensive 
care unit. Annals of Intensive Care 2011;1:47. doi:10.1186/2110-5820-1-47. 
2. Vincent JL, Rello J, Marshall J, et al. International study of the prevalence and outcomes of 
infection in intensive care units. JAMA 2009;302:2323-2329. 
3. Kalil AC, Metersky ML, Klompas M, et al. Management of Adults With Hospital-acquired and 
Ventilator-associated Pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases 
Society of America and the American Thoracic Society. Clin Infect Dis 2016;63(5):e61. 
4. Stebbings AE, Ti TY, Tan WC. Hospital acquired pneumonia in the medical intensive care unit--a 
prospective study. Singapore Med J. 1999 Aug;40(8):508-12. 
5. Y Arabia, N Al-Shirawia, Z Memishb, et al. Ventilator-associated pneumonia in adults in developing 
countries: a systematic review Int J Infec Dis 2008;12(5): 505–512.  
6. Muscedere JG, Day A, Heyland DK. Mortality, attributable mortality, and clinical events as end 
points for clinical trials of ventilator-associated pneumonia and hospital-acquired pneumonia. Clin 
Infect Dis 2010;51:S120-5. 
7. Kollef MH, Hamilton CW, Ernst FR. Economic impact of ventilator-associated pneumonia in a large 
matched cohort. Infect Control Hosp Epidemiol 2012;33(3):250-6.  
8. N Fabregas, S Ewig, A Torres, et al. Clinical diagnosis of ventilator associated pneumonia revisited: 
comparative validation using immediate post-mortem lung biopsies. Thorax 1999; 54:867-873. 
9. Hill JD, JL Ratliff, J C Parrott, et al. Pulmonary pathology in acute respiratory insufficiency: lung 
biopsy as a diagnostic tool. J Thoracic Cardiovas Surg 1976;71:64-71. 
10. Chastre J, Wolff M, Fagon JY, et al. Comparison of 8 vs 15 days of antibiotic therapy for ventilator-
associated pneumonia in adults: a randomized trial. JAMA 2003; 19;290(19):2588-98. 
11. Capellier G, Mockly H, Charpentier C, et al. Early-Onset Ventilator-Associated Pneumonia in Adults 
Randomized Clinical Trial: Comparison of 8 versus 15 Days of Antibiotic Treatment. PLoS ONE 2012; 
7(8): e41290. 
12. C Luyt, N Bréchot, J Trouillet et al. Antibiotic stewardship in the intensive care unit. Crit Care 
2014;18:480. 
13. Jones RN. Microbial etiologies of hospital-acquired bacterial pneumonia and ventilator-associated 
bacterial pneumonia. Clin Infect Dis 2010;51 Suppl 1:S81-7.  
14. Nhu NT, Lan NP, Campbell JI, et al. Emergence of carbapenem-resistant Acinetobacter baumannii 
as the major cause of ventilator-associated pneumonia in intensive care unit patients at an 
infectious disease hospital in southern Vietnam. J Med Microbiol. 2014;63:1386–1394. 
15. A Vasudevan, L Chuang, J Li, A Mukhopadhyay, EYY Goh, PA. Tambyah. Inappropriate empirical 
antimicrobial therapy for multidrug-resistant organisms in critically ill patients with pneumonia is 
not an independent risk factor for mortality: Results of a prospective observational study of 758 
patients. J Glob Antimicrob Resist. 2013;3: 123–130.  
16. P Rattanaumpawan, J Lorsutthitham, P Ungprasert, N Angkasekwinai, V Thamlikitkul. Randomized 
controlled trial of nebulized colistimethate sodium as adjunctive therapy of ventilator-associated 
pneumonia caused by Gram-negative bacteria. J Antimicrob Chemother. 2010; 65(12): 2645-2649.  
17. Inchai J, Pothirat C, Liwsrisakun C, Deesomchok A, Kositsakulchai W, Chalermpanchai N. Ventilator-
associated pneumonia: epidemiology and prognostic indicators of 30-day mortality. Jpn J Infect 
Dis. 2015;68(3):181-6.  

Protocol version 5.1 dated 28 July 2021 
 
Page 26 of 30 
 
18. W Reechaipichitkul, S Phondongnok, J Bourpoern, et al. Causative agents and resistance among 
hospital-acquired and ventilator-acquired pneumonia at Srinagarind Hospital, Northeastern 
Thailand. Southeast Asian J Trop Med Public Health 2013;44(3):490-502. 
19. Kiratisin, Pattarachai et al. Comparative in vitro activity of carbapenems against major Gram-
negative pathogens: results of Asia-Pacific surveillance from the COMPACT II study. Int J 
Antimicrob Agents. 2012;39(4):311-6. 
20. White AC Jr, Atmar RL, Wilson J, Cate TR, Stager CE, Greenberg SB. Effects of requiring prior 
authorization for selected antimicrobials: expenditures, susceptibilities, and clinical outcomes. Clin 
Infect Dis. 1997;25(2):230-9. 
21. Pakyz AL, Oinonen M, Polk RE. Relationship of carbapenem restriction in 22 university teaching 
hospitals to carbapenem use and carbapenem-resistant Pseudomonas aeruginosa. Antimicrob 
Agents Chemother 2009; 53:1983–6. 
22. Lewis GJ, Fang X, Gooch M, Cook PP. Decreased resistance of Pseudomonas aeruginosa with 
restriction of ciprofloxacin in a large teaching hospital’s intensive care and intermediate care units. 
Infect Control Hosp Epidemiol 2012; 33:368–73. 
23. Jessina C. McGregor, J P Furuno. Antimicrobial stewardship: Patients over process: Optimizing 
Research Methods Used for the Evaluation of Antimicrobial Stewardship Programs. Clin Infect Dis. 
2014;59(S3): S185-S192. 
24. Schuts EC, Hulscher ME, Mouton JW et al. Current evidence on hospital antimicrobial stewardship 
objectives: a systematic review and meta-analysis. Lancet Infect Dis. 2016;16(7):847-56. 
25. Kardaś-Słoma L, Boëlle P-Y, Opatowski L, Guillemot D, Temime L. Antibiotic Reduction Campaigns 
Do Not Necessarily Decrease Bacterial Resistance: the Example of Methicillin-Resistant 
Staphylococcus aureus. Antimicrob Agents Chemother. 2013;57(9):4410-4416.  
26. Bal AM, Gould IM. Antibiotic stewardship: overcoming implementation barriers. Curr Opin Infect 
Dis. 2011;24(4):357-62.  
27. Howard P, Pulcini C, Levy Hara G, et al. An international cross-sectional survey of antimicrobial 
stewardship programmes in hospitals. J Antimicrob Chemother 2015; 70: 1245–55. 
28. L Caudill, JR Wares. The Role of Mathematical Modeling in Designing and Evaluating Antimicrobial 
Stewardship Programs. Curr Treat Options Infect Dis. 2016; 8:124–138.  
29. Centers for Disease Control and Prevention. Pneumonia (Ventilator-associated [VAP] and non-
ventilator-associated Pneumonia [PNEU]) Event. January 2017. Retrieved from 
https://www.cdc.gov/nhsn/pdfs/pscmanual/6pscvapcurrent.pdf  
30. Fabregas N, Ewig S, Torres A, Al-Abiary M, Ramirez J, de La Bellacasa JP, Bauer T, Cabello H: Clinical 
diagnosis of ventilator associated pneumonia revisited: comparative validation using immediate 
post-mortem lung biopsies. Thorax 1999, 54: 867-873. 
31. Brun-Buisson C, Fartoukh M, Lechapt E, et al. Contribution of blinded, protected quantitative 
specimens to the diagnostic and therapeutic management of ventilator-associated pneumonia. 
Chest 2005; 128:533–44.  
32. Raman K, Nailor MD, Nicolau DP, Aslanzadeh J, Nadeau M, Kuti JL. Early antibiotic discontinuation 
in patients with clinically suspected ventilator-associated pneumonia and negative quantitative 
bronchoscopy cultures. Crit Care Med 2013; 41:1656–63. 
33. Singh N, Rogers P, Atwood CW, Wagener MM, Yu VL: Short-course empiric antibiotic therapy for 
patients with pulmonary infiltrates in the intensive care unit. A proposed solution for 
indiscriminate antibiotic prescription. Am J Respir Crit Care Med 2000, 162: 505-511. 

Protocol version 5.1 dated 28 July 2021 
 
Page 27 of 30 
 
34. Scott T. Micek; Suzanne Ward; Victoria J. Fraser. A Randomized Controlled Trial of an Antibiotic 
Discontinuation Policy for Clinically Suspected Ventilator Associated Pneumonia. Chest. 2004 
May;125(5):1791-9. 
35. Mandell LA, Wunderink RG, Anzueto A, et al; Infectious Diseases Society of America; American 
Thoracic Society. Infectious Diseases Society of America/American Thoracic Society consensus 
guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis. 
2007;44(suppl 2):S27-S72. 
36. Canadian Critical Care Trials Group: A randomized trial of diagnostic techniques for ventilator-
associated pneumonia. N Engl J Med 2006, 355: 2619-2630. 
37. Berton DC, Kalil AC, Cavalcanti M, Teixeira PJ: Quantitative versus qualitative cultures of 
respiratory secretions for clinical outcomes in patients with ventilator-associated pneumonia 
Cochrane Database Syst Rev CD006482. 2012. 
38. Jones AE, Trzeciak S, Kline JA. The Sequential Organ Failure Assessment score for predicting 
outcome in patients with severe sepsis and evidence of hypoperfusion at the time of emergency 
department presentation. Critical care medicine. 2009;37(5):1649-1654. 
39. U.S. Department of Health and Human Services Food and Drug Administration. Non-Inferiority 
Clinical Trials to Establish Effectiveness Guidance for Industry. November 2016. Available at: 
https://www.fda.gov/media/78504/download 
40. Piaggio G, Elbourne DR, Pocock SJ, Evans SJW, Altman DG, CONSORT Group  for the. Reporting of 
Noninferiority and Equivalence Randomized Trials. JAMA [Internet]. 2012 Dec 26 [cited 2018 Sep 
26];308(24):2594. Available from: 
http://jama.jamanetwork.com/article.aspx?doi=10.1001/jama.2012.87802 
41. Durrleman S, Simon R. Planning and monitoring of equivalence studies. Biometrics.1990;46:329-
336. 
42. Moi Lin Ling, Anucha Apisarnthanarak, Gilbert Madriaga; The Burden of Healthcare-Associated 
Infections in Southeast Asia: A Systematic Literature Review and Meta-analysis, Clin Infect Dis. 
2015; 60 (11): 1690–1699. 
 
 

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17. APPENDIX A:  STUDY FLOW CHART  
 
 
1. Patients who satisfy all the inclusion criteria below may be recruited:  
a. 
Patients 18 years and older, and 
b. 
Invasive mechanical ventilation ≥ 48 hours, and 
c. 
Satisfy the US Centers for Disease Control and Prevention National Healthcare Safety Network VAP 
diagnostic criteria [29] 
o 
At least one of the following:  
1. temperature > 38 °C  
2. white blood cell count ≥ 12,000 cells/mm3 or ≤ 4,000 cells/mm3 
3. altered mental status with no other causes in >70 year-olds; and  
o 
Two or more chest imaging tests demonstrating at least one of the following:  
1. new and progressive OR progressive and persistent infiltrate 
2. new and persistent OR progressive and persistent consolidation 
3. new and persistent OR progressive and persistent cavitation, and  
o 
At least two of the following:  
1. new onset of purulent sputum, or change in character of sputum, or increased 
respiratory secretions, or increased in suctioning requirements 
2. new onset or worsening tachypnea or dyspnea 
3. rales or bronchial breath sounds 
4. worsening gas exchange defined by oxygen desaturations (e.g., PaO2/FiO2 <240), 
increased oxygen requirements or increased ventilation demand  
Clinically suspected VAP according to US CDC criteria1
Enrollment
Assessment with 
respiratory culture2 report 
and clinical criteria of 
stability, exclusion if new 
exclusion criteria met3
Randomisation  if criteria 
to stop antibiotics met 
Control (long) arm
Physician preference to 
stop 
Intervention (short) arm
Stop antibiotics

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2. Respiratory cultures can be quantitative or non-quantitative, invasive or non-invasive.  
3. For those participants randomised to the intervention (short duration) arm, site investigators should 
assess the participants daily. Antibiotics should be stopped, if the criteria below are satisfied, 
a. body temperature was ≤ 38.3°C  (core body temperature measured orally or rectally) or 38.0°C 
(axillary) for 48 hours, and 
b. hemodynamic instability (systolic blood pressure ≥ 90 mm Hg without inotropic support or no 
requirement of inotropic support to maintain systolic blood pressure above 90 mm Hg). 
 
 
 

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18. APPENDIX B:  SCHEDULE OF STUDY PROCEDURES 
Procedures 
Visit timing 
Day 0 
Daily during 
hospitalisation 
Weekly during 
hospitalisation 
Day 28/60 (+5) 
Screening 
and 
enrolment 
Follow up visit/ 
Last visit 
Informed consent 
X 
 
 
 
Demographics 
X 
 
 
 
Medical history and 
medical record review 
X 
X 
X 
X 
Review antibiotics 
administration records 
X 
X 
X 
X 
Physical examination 
X 
 
 
 
Eligibility assessment 
X 
 
 
 
Randomisation once 
clinical criteria for 
stability met 
 
X 
 
 
Respiratory microbiology 
culture  
X 
 
 
 
Stool and sputum sample 
for microbiome study  
X 
 
X 
X 
Review of antibiotics and 
stop antibiotics if criteria 
fulfilled  
 
X 
 
 
Adverse event 
assessments (throughout 
the study) 
 
X 
X 
X