Two doses of the Pfizer/BioNTech COVID-19 vaccine has proven to be less effective in children aged five to 11, data revealed by New York state officials on Monday shows.
According to the study published on medRxiv, the vaccine provided almost no protection against contracting the coronavirus for children aged five to 11, even within a month of receiving their second shot. The vaccine was effective, however, in preventing severe illness and hospitalisation in that age group.
Researchers at the New York State Department Health gauged infection rates of minors who have had the Pfizer jab made available to them. Children were split into two age groups, one of children five to 11 and the other children from 12 to 17.
The study, yet to be peer-reviewed found that during the Omicron era, the effectiveness of the Pfizer-BioNTech Covid vaccine declined rapidly -- from 68 per cent to 12 per cent for children aged 5-11 years.
Vaccine efficacy also declined from 66 per cent to 51 per cent for those between 12 and 17 years.
The six New York state public health scientists who led the study analyzed cases and hospitalization rates from 13 December 2021 to 30 January 2022 among 852,384 fully vaccinated children aged 12 to 17 and 365,502 fully vaccinated children aged five to 11.
Eli Rosenberg, the New York state deputy director for science, told the New York Times that although it was disappointing to see the decline in vaccine effectiveness, it should be acknowledged that the Pfizer/BioNTech shot was developed in response to an earlier virus variant.
"It looks very distressing to see this rapid decline but it's again all against Omicron," he said.
Additional research was needed, he said, to determine the best dose to administer to children, taking into consideration factors such as the number and timing of shots.
News of the research came shortly after the Centers for Disease Control and Prevention (CDC) outlined new mask guidelines for more than 70% of the US population.