Now, a large study out of Argentina is reinforcing the call to ensure children are vaccinated against COVID-19 to prevent death. The study published today in The British Medical Journal (BMJ), finds that the vaccines remain effective in preventing death in adolescents and children, regardless of which variants are predominant (Delta, Omicron, etc.).
While vaccine effectiveness for infection can decrease over time, particularly when the Omicron variant emerged one year ago, research from a team representing three institutions in Argentina finds that vaccinations continue to prevent deaths and remain and important public health measure.
It has been well established that both mRNA vaccines and inactivated COVID-19 vaccines are effective in preventing severe disease and infection in children and adolescents. Also, waning protection against infection has been studied, especially from mRNA vaccines (such as the Moderna and Pfizer-BioNTech vaccines), but hasn’t been examined as much in the inactivated vaccines in children like Sinopharm and Sinovac-CoronaVac.
In an effort to fill in this knowledge gap, the team examined the effectiveness of two mRNA vaccines and an inactivated vaccine to see how they fared against both COVID-19 related infection and death, and also how immunity waned over a shorter period of time in adolescents and children.
In August 2021, Argentina started vaccinating 12 to 17 year-olds and children age 3 to 11 followed in October 2021.
For this study, the team used data for 844,460 children and adolescents (age 3 to 17) collected by the National Surveillance System and the Nominalized Federal Vaccination Registry of Argentina. Before being tested for COVID-19 via a PCR and rapid antigen test, the participants were grouped by vaccination status. They data was collected from September 2021 to April 2022, when the Delta and Omicron BA.1 variants were dominant in Argentina.
The fully vaccinated 12 to 17 year-olds received two doses of either the Moderna or Pfizer-BioNTech mRNA vaccines, and fully vaccinated 3 to 11 year-olds received two doses of inactivated Sinopharm vaccine.
The participants who tested positive (categorized as cases) were matched to those who tested negative (categorized as controls) by sex, age, week of testing, type of test, area of residence, and any existing health conditions. After this matching process, 139,321 cases along with their corresponding controls were analyzed.
According to the results, estimated vaccine effectiveness against COVID-19 infection was 61 percent in children and 67 percent in adolescents during the Delta wave, but dropped to 16 percent in children and 26 percent in adolescents during the Omicron wave.
The report also showed that vaccine effectiveness did decline over time, particularly with Omicron, from 38 percent effective at 15 to 30 days after vaccination to 2 percent after 60 days or more in children and from 56 percent effective to 12 percent in adolescents.
The vaccines effectiveness in preventing death related to an infection during the Omicron wave held strong at 67 percent in children and 98 percent in adolescents.
The researchers caution that this is an observational study that can’t directly establish cause and that some of the information, including hospital admissions or symptoms, was incomplete. They also can’t rule out the possibility that other factors not measured in their study may have affected the final results.
However, the team found that these results remained the same after further analyses that assessed how different tests and vaccine combinations impacted the numbers and that the results are in line with similar studies.
“In summary, vaccinating children is an important public health measure that will prevent mortality in this population, especially in periods of high viral circulation,” the team concludes in a statement. They also stress the importance of vaccination for preventing death in children and adolescents with COVID-19 regardless of the circulating variant.
