Resuming global childhood vaccination campaigns during the COVID-19 pandemic

New research published on the medRxiv* preprint server suggests childhood vaccination to prevent other infectious diseases has plummeted during the pandemic. The decrease appears to stem from the suspension of health campaigns promoting immunization and the risk of catching the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative pathogen of coronavirus disease 2019 (COVID-19).

Led by Mark Jit of the London School of Hygiene and Tropical Medicine, UK, the research team found taking precautions — wearing masks, getting a COVID-19 diagnostic test if symptoms present — and campaign timing can reduce the risk of SARS-CoV-2 vaccination to all parties involved.

The researchers write:

We find that the SARS-CoV-2 infection risks to vaccinators, vaccinees, and their caregivers from a vaccine campaign conducted during a COVID-19 epidemic can vary considerably depending on the circumstances under which a campaign is conducted...Our findings support the continuation of vaccination campaigns using adequate risk mitigation during the COVID-19 pandemic, rather than cancelling them entirely.”

Gathering their data

The researchers performed a modeling study using population age-structure and contact patterns from Burkina Faso, Ethiopia, and Chile. The countries were selected for having the lowest, median, and highest population median age among countries with a measles vaccination campaign planned for 2020. They combined their data with a SARS-CoV-2 transmission model to evaluate the level of risk when undergoing vaccination.

The model ran for two years, with the first simulation week depicting the start of the pandemic. “Our objective was not to predict the actual SARSCoV-2 epidemics experienced by these particular countries, but rather to generate plausible scenarios using alternative demography and contact patterns to examine the implications for the risk associated with vaccination campaigns,” wrote the team.

Factors that were taken into account included the spread of SARS-CoV-2, the number of vaccinations available, how long the campaign was, screening for COVID-19, and the effectiveness of personal protective equipment (PPE).

What they found

Their modeling results showed similar SARS-CoV-2 incidences with 29%-39% infected by the end of the first year.

Having a high prevalence of SARS-CoV-2 infections in the local community and at the time of the vaccination campaign increased the infection risk for people administering vaccines, children, and caregivers.

Not having the proper PPE or insufficient screening of potential COVID-19 symptoms resulted in an estimated 32% to 58% infection risk for vaccinators and a 0.30% to 0.90% for children and their caregivers.

Having a 75% effectiveness in using PPE, the infection risk drops to 10% to 22% for vaccinators and 0.15% to 0.41% for children and caregivers.

Symptomatic screening in the absence of PPE slightly reduced infection, but not as much as having PPE available. Screenings caused a 3% to 6% reduction in vaccinators’ infection risk and a 0.02% to 0.16% reduction for children and caregivers.

Having PPE that was 90% effective in blocking SARS-CoV-2 transmission further reduced risk to 3.6%-8% in vaccinators. However, the risk reduction only somewhat reduced infection risk for vaccinees.

Performing vaccination at a person’s household lowered the infection risk for both vaccinators and vaccinees. The researchers suggest this is because people are reducing community contacts who travel to or present in the local vaccination site.

Having PPE with the highest effectiveness at blocking SARS-CoV-2 was the most beneficial in reducing infection risk for vaccinees and caregivers. After effective PPE, other factors that reduce risk include a shorter vaccination campaign, shorter infectious period, or a more extended latent infection period.

Study limitations

While lowering the risk of COVID-19 infection is higher when there is less SARS-CoV-2 circulating in the area, the researchers acknowledge that low- and middle-income countries may have inaccuracies in their local reporting data for COVID-19 cases — with people relying more on anecdotal accounts. They argue that official country-wide numbers may not translate to local incidences in various parts of the region.

A second study limitation is that the research results remain unclear on what type of PPE— think of the effectiveness of an N95 mask versus a cloth mask versus a surgical mask — would be most beneficial in mitigating risk. There’s also a lack of specificity on what type of training and adherence is necessary for limiting the danger of infection during vaccination campaigns.

*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:
Jocelyn Solis-Moreira

Written by

Jocelyn Solis-Moreira

Jocelyn Solis-Moreira graduated with a Bachelor's in Integrative Neuroscience, where she then pursued graduate research looking at the long-term effects of adolescent binge drinking on the brain's neurochemistry in adulthood.


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