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
Venue: medRxiv
Year: 2020

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.  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.  For every one excess Covid 19 death attributable to SARS CoV 2 infections acquired during routine vaccination clinic visits, there could be 143 (38 576) 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 58,000 (3,200 21,350,000) 52,000 (2,800 18,884,000) 2,000 (393 12,000) and 157 (41 652) 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 5 (1 21) under these highly conservative assumptions and if the risk to only the vaccinated children is considered, the benefit risk ratio is 2,000 (131 839,000)  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. 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.