Benefit-risk analysis of health benefits of routine childhood immunisation against the excess risk of SARS-CoV-2 infections during the COVID-19 pandemic in Africa
Authors: Abbas Kaja , Procter Simon R , van Zandvoort Kevin , Clark Andrew , Funk Sebastian ,   LSHTM CMMID CMMID COVID-19 Working Group, Mengistu Tewodaj , Hogan Dan , Dansereau Emily , Jit Mark , Flasche Stefan 
Published: May 2020

Background

National immunisation programmes globally are at risk of suspension due to the severe health system constraints and physical distancing measures in place to mitigate the ongoing COVID-19 pandemic. Our aim is to compare the health benefits of sustaining routine childhood immunisation in Africa against the risk of acquiring SARS-CoV-2 infections through visiting routine vaccination service delivery points.

Methods

We used two scenarios to approximate the child deaths that may be caused by immunisation coverage reductions during COVID-19 outbreaks. First, we used previously reported country-specific child mortality impact estimates of childhood immunisation for diphtheria, tetanus, pertussis, hepatitis B, Haemophilus influenzae type b, pneumococcal, rotavirus, measles, meningitis A, rubella, and yellow fever (DTP3, HepB3, Hib3, PCV3, RotaC, MCV1, MCV2, MenA, RCV, YFV) to approximate the future deaths averted before completing five years of age by routine childhood vaccination during a 6-month COVID-19 risk period without catch-up campaigns. Second, we analysed an alternative scenario that approximates the health benefits of sustaining routine childhood immunisation to only the child deaths averted from measles outbreaks during the COVID-19 risk period. The excess number of infections due to additional SARS-CoV-2 exposure during immunisation visits assumes that contact reducing interventions flatten the outbreak curve during the COVID-19 risk period, that 60% of the population will have been infected by the end of that period, that children can be infected by either vaccinators or during transport and that upon child infection the whole household would be infected. Country specific household age structure estimates and age dependent infection fatality rates are then applied to calculate the number of deaths attributable to the vaccination clinic visits. We present benefit-risk ratios for routine childhood immunisation alongside 95% uncertainty range estimates from probabilistic sensitivity analysis.

Findings

For every one excess COVID-19 death attributable to SARS-CoV-2 infections acquired during routine vaccination clinic visits, there could be 84 (14-267) deaths in children prevented by sustaining routine childhood immunisation in Africa. The benefit-risk ratio for the vaccinated children, siblings, parents or adult care-givers, and older adults in the households of vaccinated children are 85,000 (4,900 - 546,000), 75,000 (4,400 - 483,000), 769 (148 - 2,700), and 96 (14 - 307) respectively. In the alternative scenario that approximates the health benefits to only the child deaths averted from measles outbreaks, the benefit-risk ratio to the households of vaccinated children is 3 (0 - 10) under these highly conservative assumptions and if the risk to only the vaccinated children is considered, the benefit-risk ratio is 3,000 (182 - 21,000).

Interpretation

Our analysis suggests that the health benefits of deaths prevented by sustaining routine childhood immunisation in Africa far outweighs the excess risk of COVID-19 deaths associated with vaccination clinic visits, especially for the vaccinated children. However, there are other factors that must be considered for strategic decision making to sustain routine childhood immunisation in African countries during the COVID-19 pandemic. These include logistical constraints of vaccine supply chain problems caused by the COVID-19 pandemic, reallocation of immunisation providers to other prioritised health services, healthcare staff shortages caused by SARS-CoV-2 infections among the staff, decreased demand for vaccination arising from community reluctance to visit vaccination clinics for fear of contracting SARS-CoV-2 infections, and infection risk to healthcare staff providing immunisation services as well as to their households and onward SARS-CoV-2 transmission into the wider community.

Funding

Gavi, the Vaccine Alliance and Bill & Melinda Gates Foundation (OPP1157270)

Research in context

Evidence before the study

National immunisation programmes globally are at risk of disruption due to the severe health system constraints caused by the ongoing COVID-19 pandemic and the physical distancing measures to mitigate the outbreak. The decrease in vaccination coverage increases the proportion of susceptible children at risk of increased morbidity and mortality from vaccine-preventable disease outbreaks. Outbreaks of vaccine preventable disease have been observed during previous interruptions to routine immunisation services during an ongoing infectious disease epidemic, such as during the 2013-2016 Ebola outbreak in West Africa, when most health resources were shifted towards the Ebola response which led to decreasing vaccination coverage and consequently outbreaks of measles and other vaccine-preventable diseases.

Added value of this study

We estimated the benefit-risk ratio by comparing the deaths prevented by sustaining routine childhood immunisation for diphtheria, tetanus, pertussis, hepatitis B, Haemophilus influenzae type b, pneumococcal, rotavirus, measles, meningitis A, rubella, and yellow fever vaccines with the excess COVID-19 deaths associated with vaccination clinic visits. The benefit of routine childhood immunization programmes in all the 54 countries of Africa is higher than the COVID-19 risk associated with these vaccination clinic visits.

Implications of all the available evidence

Routine childhood immunisation programmes should be safeguarded for continued service delivery and prioritised for the prevention of infectious diseases, as logistically possible, as part of delivering essential health services during the COVID-19 pandemic in Africa. The current immunisation service models will require adaptation, including physical distancing measures, personal protective equipment, and good hygiene practices for infection control at the vaccination clinics, and have to be complemented by new immunisation service models for sustaining routine childhood immunisation in the African countries during the COVID-19 risk period.