Regardless of the variant, vaccine efficacy remains high in children

The efficacy of COVID-19 vaccines in preventing death continues to be high in children and adolescents, regardless of the predominant circulating variant, as suggested by a large study conducted in Argentina and published in the scientific journal ‘The BMJ’.

Although vaccine effectiveness against the infection has declined considerably over time, especially during the Omicron period, the researchers say vaccinating children is an important public health measure that will continue to prevent deaths.

This is already known COVID-19 mRNA vaccines are effective in preventing serious illness and infection in children and adolescentsbut data on deaths are lacking.

Reduced protection against infection has also been described, particularly for mRNA vaccines, but the evidence for inactivated vaccines in children is limited.

To fill this knowledge gap, the researchers evaluated the efficacy of two mRNA vaccines (Moderna and Pfizer-BioNTech) and Sinopharm’s inactivated vaccine against COVID-19-related infection and death and decreased immunity short-term, in children and adolescents.

Their conclusions are based on data from 844,460 children and adolescents (ages 3 to 17) from Argentina’s National Surveillance System and Federal Vaccination Registry. Argentina started vaccinating adolescents (12-17 years) in August 2021 and young children (3-11 years) in October 2021.

Participants were matched for vaccination status before being tested for COVID-19 (by PCR or rapid antigen test) at a medical center from September 2021 to April 2022, when BA.1 delta and omicron variants were dominant in Argentina.

The fully vaccinated children aged 12 to 17 received two doses of Pfizer-BioNTech and/or Moderna vaccines and the fully vaccinated children aged 3 to 11 received two doses of Sinopharm vaccine. The median time from the second dose to testing was 66 days for children aged 12 to 17 years and 54 days for those aged 3 to 11 years.

Those who tested positive (cases) were matched with those who tested negative (controls) by age, gender, area of ​​residence, week of testing, type of test, and existing health conditions. After matching, 139,321 cases with matched controls were included for analysis.

The results show that the estimated vaccine efficacy against COVID-19 infection was 61% in children and 67% in adolescents. during the Delta Period and 16 and 26 percent, respectively, during the Omicron Period.

Vaccine efficacy decreased over time, especially during the omicron period, from 38% at 15 to 30 days after vaccination to 2% after 60 days or more in children and 56 to 12% in adolescents.

Vaccine efficacy against COVID-19 infection-related death during the omicron period was 67% in children and 98% in adolescents.

This is an observational study and as such cannot establish cause. Additionally, the researchers acknowledge that some data, such as symptoms and hospital admissions, were incomplete. Furthermore, they cannot rule out the possibility that other unmeasured factors (confounders) may have influenced their results.

However, their results were consistent after further analyzes to evaluate the impact of different tests and vaccine combinations and are in line with those of other similar studies, suggesting they may be robust.

For this reason, researchers say that vaccination is effective in preventing the death of children and adolescents with COVID-19, regardless of the circulating variant.

Furthermore, they add that the vaccines are also effective in preventing COVID-19 infection in children and adolescents in the short term, although a significant decline has been observed over time, especially during omicron dominance.

“In summary, vaccinating children is an important public health measure that will prevent mortality in this population, especially in periods of high viral circulation.“concluded the authors.