The importance of supplementary immunisation activities to prevent measles outbreaks during the COVID-19 pandemic in Kenya

Abstract

Background The COVID-19 pandemic has disrupted routine measles immunisation and supplementary immunisation activities (SIAs) in most countries including Kenya. We assessed the risk of measles outbreaks during the pandemic in Kenya as a case study for the African Region. Methods Combining measles serological data, local contact patterns, and vaccination coverage into a cohort model, we predicted the age-adjusted population immunity in Kenya and estimated the probability of outbreaks when contact-reducing COVID-19 interventions are lifted. We considered various scenarios for reduced measles vaccination coverage from April 2020. Results In February 2020, when a scheduled SIA was postponed, population immunity was close to the herd immunity threshold and the probability of a large outbreak was 34% (8–54). As the COVID-19 contact restrictions are nearly fully eased, from December 2020, the probability of a large measles outbreak will increase to 38% (19–54), 46% (30–59), and 54% (43–64) assuming a 15%, 50%, and 100% reduction in measles vaccination coverage. By December 2021, this risk increases further to 43% (25–56), 54% (43–63), and 67% (59–72) for the same coverage scenarios respectively. However, the increased risk of a measles outbreak following the lifting of all restrictions can be overcome by conducting a SIA with ≥ 95% coverage in under-fives. Conclusion While contact restrictions sufficient for SAR-CoV-2 control temporarily reduce measles transmissibility and the risk of an outbreak from a measles immunity gap, this risk rises rapidly once these restrictions are lifted. Implementing delayed SIAs will be critical for prevention of measles outbreaks given the roll-back of contact restrictions in Kenya.

Inequities in childhood immunisation coverage associated with socioeconomic, geographic, maternal, child, and place of birth characteristics in Kenya

“…The COVID-19 pandemic has disrupted routine childhood immunisation and led to the suspension of supplementary immunisation activities in many countries including Kenya [44–46]. Immunisation services have been disrupted in both fixed post and outreach immunisation activities due to health workers being redeployed to the COVID-19 response and parents being unable or unwilling to bring their children into health facilities because of restrictions on movements, economic hardships, or the fear of contracting SARS-CoV-2 while attending health facilities, among other reasons [44].…”

Childhood Immunisation Coverage in Kenya by Socioeconomic, Geographic, Maternal, Child, and Place of Birth Characteristics: Equity Impact Analysis

“…1 shows full immunisation coverage in the eight regions (defunct provinces) of Kenya. Full immunisation coverage ranged from 42% [36][37][38][39][40][41][42][43][44][45][46][47][48][49] in the North Eastern region to 78% [72][73][74][75][76][77][78][79][80][81][82][83] in the Central and Eastern regions. Ethnicity and religion was excluded from the multivariable logistic regression analysis due to collinearity with the region of residence -ethnic groups in Kenya tend to cluster in specific regions, and while the predominant religion in Kenya is Christianity, Muslims are predominantly based in the Coastal and North Eastern regions.…”

“…The COVID-19 pandemic has disrupted routine childhood immunisation and led to the suspension of supplementary immunisation activities in many countries including Kenya [44][45][46]. Immunisation services have been disrupted in both fixed post and outreach immunisation activities due to health workers being redeployed to the COVID-19 response and parents being unable or unwilling to bring their children into health facilities because of restrictions on movements, economic hardships, or the fear of contracting SARS-CoV-2 while attending health facilities, among other reasons [44].…”

“…Figure 1shows full immunisation coverage in the eight regions (defunct provinces) of Kenya. Full immunisation coverage ranged from 42%[36][37][38][39][40][41][42][43][44][45][46][47][48][49] in the North Eastern region to 78%[72-83] in the Central and Eastern regions.…”

Disruptions to childhood immunisation due to the COVID-19 pandemic

“…Although physical distancing measures due to the COVID-19 pandemic might have reduced the transmission of childhood infectious diseases, the risk of vaccine-preventable disease outbreaks among children will increase as COVID-19-related mitigation measures are lifted. 12 Therefore, we commend Causey and colleagues 1 for generating this timely evidence and these modelled estimates of disruptions to childhood immunisation as a result of the COVID-19 pandemic, which are important for inferring immunity gaps and epidemiological risk assessment of vaccine-preventable disease outbreaks among children in the future. We recommend national immunisation programmes to act upon this valuable evidence for planning and implementation of catch-up vaccination services to close the immunity gaps, to avoid reversing the substantial gains from childhood immunisation in reducing mortality and morbidity globally.…”