Sustained reductions in life-threatening invasive bacterial diseases during the first two years of the COVID-19 pandemic: analyses of prospective surveillance data from 30 countries participating in the IRIS Consortium
Authors: Shaw David , Abad Raquel , Amin-Chowdhury Zahin , Bautista Adriana , Bennett Desiree , Broughton Karen , Cao Bin , Casanova Carlo , Choi Eun Hwa , Chu Yiu-Wai , Claus Heike , Coelho Juliana , Corcoran Mary , Cottrell Simon , Cunney Robert , Cuypers Lize , Dalby Tine , Davies Heather , de Gouveia Linda , Deghmane Ala-Eddine , Demczuk Walter , Desmet Stefanie , Domenech Mirian , Drew Richard , du Plessis Mignon , Duarte Carolina , Erlendsdóttir Helga , Fry Norman , Fuursted Kurt , Hale Thomas , Henares Desiree , Henriques-Normark Birgitta , Hilty Markus , Hoffmann Steen , Humphreys Hilary , Ip Margaret , Jacobsson Susanne , Johnson Christopher , Johnston Jillian , Jolley Keith A , Kawabata Aníbal , Kozakova Jana , Kristinsson Karl G , Krizova Pavla , Kuch Alicja , Ladhani Shamez , Lâm Thiên-Trí , María Eugenia León , Lindholm Laura , Litt David , Maiden Martin CJ , Martin Irene , Martiny Delphine , Mattheus Wesley , McCarthy Noel D , McElligott Martha , Meehan Mary , Meiring Susan , Mölling Paula , Morfeldt Eva , Morgan Julie , Mulhall Robert , Muñoz-Almagro Carmen , Murdoch David , Murphy Joy , Musilek Martin , Mzabi Alexandre , Novakova Ludmila , Oftadeh Shahin , Perez-Arguello Amaresh , Pérez-Vázquez Maria , Perrin Monique , Perry Malorie , Prevost Benoit , Roberts Maria , Rokney Assaf , Ron Merav , Sanabria Olga Marina , Scott Kevin J , Sheppard Carmen , Siira Lotta , Sintchenko Vitali , Skoczyńska Anna , Sloan Monica , Slotved Hans-Christian , Smith Andrew J , Steens Anneke , Taha Muhamed-Kheir , Toropainen Maija , Tzanakaki Georgina , Vainio Anni , van der Linden Mark PG , van Sorge Nina M , Varon Emmanuelle , Vohrnova Sandra , Gottberg Anne von , Yuste Jose , Zanella Rosemeire , Zhou Fei , Brueggemann Angela B 
Published: December 2022

Background

The Invasive Respiratory Infection Surveillance (IRIS) Consortium was established to assess the impact of the COVID-19 pandemic on invasive diseases caused byStreptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidisandStreptococcus agalactiae. Here we analyse the incidence and distribution of disease during the first two years of the pandemic.

Methods

Laboratories in 30 countries/territories representing five continents submitted case data from 2018-2021 to private projects within databases in PubMLST. The impact of COVID-19 containment measures on the overall number of cases was analysed, and changes in disease distributions by patient age and serotype/group were examined. Interrupted time series analyses quantified the impact of pandemic response measures and their relaxation on disease rates, and autoregressive integrated moving average models estimated effect sizes and forecasted counterfactual trends by hemisphere.

Findings

Overall, 116,841 cases were analysed: 76,481 (2018-2019, pre-pandemic) plus 40,360 (2020-2021, pandemic). During the pandemic there was a significant reduction in the risk of disease caused byS pneumoniae(risk ratio: 0.47; 95% confidence interval: 0.40-0.55),H influenzae(0.51; 0.40-0.66) andN meningitidis(0.26; 0.21-0.31), whereas no significant changes were observed for the non-respiratory-transmitted pathogenS agalactiae(1.02; 0.75-1.40). No major changes in the distribution of cases were observed when stratified by patient age or serotype/group. An estimated 36,289 (17,145-55,434) cases of invasive bacterial disease were averted during the first two years of the pandemic among IRIS participating countries/territories.

Interpretation

COVID-19 containment measures were associated with a sustained decrease in the incidence of invasive disease caused byS pneumoniae, H influenzaeandN meningitidisduring the first two years of the pandemic, but cases began to increase in some countries as pandemic restrictions were lifted.

Research in context

Evidence before this study

Early in the COVID-19 pandemic the IRIS Consortium reported a significant reduction in invasive disease due to respiratory-transmitted bacterial pathogens, which was associated with the implementation of COVID-19 stringency measures and changes in human social behaviour. All 26 countries/territories participating in IRIS at the time experienced a significant reduction in infections between January and May 2020, compared with the previous two years. In particular,S pneumoniaeinfections decreased by 68% at four weeks after COVID-19 containment measures were imposed, and by 82% at eight weeks.

Added value of this study

These new data from the expanded IRIS Consortium across 30 countries/territories demonstrated a sustained reduction in invasive disease throughout the first two years of the COVID-19 pandemic. Using time series modelling, we estimated that over 36,000 cases of invasive bacterial disease were averted in 2020-2021 among the countries participating in IRIS; however, minor increases in disease in the latter half of 2021 require close monitoring to understand the nature of re-emerging cases.

Implications of all the available evidence

Future epidemics and pandemics will occur, and we need to understand not only the pathogen that is directly responsible for the pandemic, but also that population-level responses to an epidemic or pandemic more broadly affect overall human health and other microbes. IRIS provides evidence for the effects of such public health responses on severe invasive bacterial infections across many countries. Moreover, these IRIS data provide a better understanding of microbial transmission, will inform vaccine development and implementation, and can contribute to healthcare service planning and provision of policies.