Findings highlight the Pfizer-BioNTech vaccine’s role in preventing MIS-C, a rare post-COVID inflammatory syndrome in children.

Study: Multisystem inflammatory syndrome in children (MIS-C) cases by vaccination status in California. Image Credit: Billion Photos/Shutterstock.com

A recent study in Vaccine analyzed public health data to assess the impact of COVID-19 vaccination on childhood multisystem inflammatory syndrome (MIS-C) in California. Examining two age groups—12-17 and 5-11 years—researchers found that vaccination significantly reduced MIS-C risk in both groups.

This study provides the first evidence of vaccine protection in younger children (5-11) and underscores the benefits of COVID-19 vaccination for children. While focusing specifically on the Pfizer-BioNTech vaccine, the findings support public health vaccination efforts.

Background

Multisystem inflammatory syndrome in children (MIS-C) is a rare medical condition that may develop one to two months following severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) infection. It afflicts about one in every 3,000 children. Still, it presents severe symptoms, including high fever, inflammation, and adverse outcomes across multiple systems, with all cases requiring hospitalization and between 1-2% of patients dying despite intensive care unit (ICU) support.

Unfortunately, little is known about MIS-C pathophysiology and the effects of vaccination on disease risk and outcomes. Vaccination against SARS-CoV-2 is hypothesized to attenuate MIS-C risk and improve outcomes, but supporting data is derived exclusively from teenagers and older children and remains limited to small cohorts.

Younger children (age group = 5-11 years) are an especially understudied population, with almost no scientific literature available on this vulnerable group.

Leveraging population-wide public health datasets would allow researchers to determine optimal public health responses to increasing MIS-C prevalence and inform policymakers, parents, and public debate in today’s increasingly anti-vaccination society.

About the study

The present study aims to address current knowledge gaps by evaluating the prevalence of MIS-C in vaccinated and unvaccinated Californian children between the ages of 5 and 17.

Population data was acquired from the California Department of Public Health (CDPH) and included clinical records archived by the California Reportable Disease Information Exchange (CalREDIE) disease surveillance system. Additionally, vaccination surveillance systems such as the California Immunization Registry, the San Diego Immunization Registry, and the Regional Immunization Data Exchange were queried for vaccination status data (date, manufacturer, batch).

Since the Pfizer-BioNTech (BNT162b2) vaccine was the first vaccine to receive necessary regulatory permissions and achieve widespread adoption across the state of California, the present study restricted its analysis only to children who received one (‘partial’ vaccination) or both (‘complete’ vaccination) dosages of the Pfizer-BioNTech vaccine. Other vaccines (such as Moderna) were excluded from analyses.

Study findings

The final older (12-17 years) study cohort comprised 872,936 unvaccinated and 2,117,575 vaccinated children (n = 2,990,511), of which 66 (0.0076%) and 51 (0.0024%) developed MIS-C.

Similar yet attenuated trends were observed in younger (5-11 years) children, with 51 cases in 2,113,725 unvaccinated children (0.0024%) and 9 cases in 1,221,293 vaccinated children (0.0007%). Children with MIS-C in California were more likely to be male than female, particularly in the younger age group.

When restricting the analyses to only participants with MIS-C and excluding children who only received partial vaccination, study findings revealed that 85% of younger MIS-C patients were unvaccinated.

This corresponds with a 3.3-fold higher incidence rate- ratio (IRR) for unvaccinated children compared to their vaccinated counterparts. Observed contrasts were even more stark in the older age group, with 90% of MIS-C patients reporting no vaccination, corresponding with a 22.9-fold higher IRR than vaccinated children.

Mortality results were similarly skewed in favor of vaccination – all 4 MIS-C-associated deaths that were obtained from public health records occurred in unvaccinated participants.

Even in participants who survived, unvaccinated children frequently experienced MIS-C presentation in 6 or more organs, substantially higher than vaccinated children. Together, these results highlight that vaccination protects both against MIS-C development and severe MIS-C outcomes.

Conclusions

The present study elucidates the protective effects of anti-SARS-CoV-2 vaccination against MIS-C risk and severity in Californian children. It supports previous data from older children (12-17 years) and presents the first evaluation of younger children (5-11 years) in vaccination-MIS-C analyses.

Study findings revealed that vaccination substantially reduced MIS-C risk across both age groups.

Additionally, none of the vaccinated children succumbed to MIS-C, compared to four unvaccinated children. Finally, disease severity was observed to be significantly attenuated in the vaccinated cohort.

Together, these findings highlight vaccination’s protective benefits against MIS-C disease risk and severity and support the ongoing government- or public health agency-promoted child vaccination campaigns.