Study reveals moderate effectiveness of Pfizer-BioNTech’s Covid-19 vaccine against Omicron in children aged 5-11

30 Jun, 2022

A large study on the effectiveness of the Pfizer-BioNTech’s Covid-19 vaccine in children aged 5-11 was published in The New England Journal of Medicine.

The study was conducted at Israel’s largest healthcare organization, Clalit Health Services, in collaboration with researchers from the University of Padua, Harvard University and University College London.

This is one of the first large observational studies that uses Real-World Data evaluate the effectiveness of the Pfizer-BioNTech BNT162b2 (Comirnaty) vaccine in children aged 5-11 against the Omicron variant. The study compared rates of Covid-19-related outcomes in 94,728 vaccinated children, with 94,728 rigorously matched unvaccinated controls.

Estimated short-term vaccine effectiveness was moderate: 51% against documented SARS-CoV-2 infection and 48% against symptomatic Covid-19 illness, during days 7-21 following the second dose. A trend towards higher effectiveness was observed among the youngest age group (5-6 year-old children) compared to the oldest age group (10-11 year-old children) within the study population. Researchers are yet to determine which part of this reduced protective effect may be attributed to the different dose formulation, and which part may be attributed to the vaccine’s ability to mount an effective response against the Omicron strain.

Previous studies revealed that the short-term effectiveness of this vaccine in preventing symptomatic Covid-19 was very high in adolescents against the Delta strain. However, there was not enough information available on vaccine effectiveness in younger children.

Researchers studied the effects of the paediatric formulation of Pfizer-BioNTech’s Covid-19 vaccine over the period of 23 November 2021 through 7 January 2022, as the Omicron (B.1.1.529) variant of SARS-CoV-2 became the dominant strain in Israel – one of the of the first countries to launch a campaign to vaccinate children 5-11 years of age.

This study represents an international collaboration of researchers from Israel, the United States and Europe, as part of the Ivan and Francesca Berkowitz Family Living Laboratory Collaboration and the VERDI Project, which is coordinated by the University of Padua, the Penta Foundation, and funded by the European Union Horizon Europe Programme.

This is the first peer-reviewed cohort study to control for differences between the two study groups across many characteristics, including demographic factors, number of chronic medical conditions and health seeking behaviour.

Findings from this study have been discussed by researchers coming from more than 30 healthcare and policy institutions worldwide, including from Israel, Haiti, South Africa, Thailand and the United States, at the VERDI General Assembly held in Padua, Italy, from 28 to 30 June 2022.

Carlo Giaquinto, Professor of Paediatrics at the Department for Woman’s and Child’s Health of the University of Padua and President of the Penta Foundation, as well as VERDI Project Coordinator, said: “This study from the Clalit data warehouse shows how Real-World Data can be used to quickly provide estimation on the effectiveness of new interventions, such as the paediatric formulation of Pfizer-BioNTech’s Covid-19 vaccine. These results present early evidence, where evidence has been limited, on how Covid-19 vaccination is also effective in the paediatric population.

Read the press release in English and Italian.


Photo by victorcoscaron from Canva