KUALA LUMPUR, March 1 – A study by New York researchers found that the efficacy of two doses of the Pfizer-BioNTech Covid-19 vaccine against infection and hospitalisation rapidly waned in children aged 5 to 11 during the Omicron wave in the state.
The study, compiled by researchers working for the New York State Department of Health, analysed health records of about 365,000 children aged 5 to 11 and over 850,000 Covid cases in adolescents aged 12 to 17 from December 13, 2021, to January 30, 2022.
The findings, which has not been peer reviewed, showed that two-dose vaccine protection against Covid infection for kids aged 5 to 11 declined from 68 per cent to 12 per cent over the period. The vaccine’s effectiveness at preventing hospitalisation in children in the younger age group fell from 100 per cent to 48 per cent.
For children aged 12 to 17 years old, vaccine effectiveness against infection dropped from 66 per cent to 51 per cent from December through the end of January. Protection against hospitalisation dropped from 85 per cent to 73 per cent for teenagers during the period.
When examining time since vaccination, vaccine efficacy against infection for children aged five to 11 years plummeted from 65 per cent at two weeks of full vaccination to just 12 per cent within 28 to 34 days, compared to a decline in protection from 76 per cent to 56 per cent for adolescents aged 12 to 17 in that period. These two groups were newly fully vaccinated from December 13 last year to January 2 this year.
The dramatic drop in vaccine effectiveness among children 5 to 11 years old was likely due to the lower dosage they received, according to a team of public health officials who carried out the study.
“Our data support vaccine protection against severe disease among children 5 to 11 years, but suggest rapid loss of protection against infection, in the Omicron variant era,” researchers wrote. “Should such findings be replicated in other settings, review of the dosing schedule for children 5-11 years appears prudent.”
The Pfizer regimen for anyone aged 12 and older is two 30-microgram shots per person. Kids aged five to 11 years old are given two 10-microgram shots, one-third the adult quantity.
In studies of children under 5, the dose is further reduced, with children aged six months to 4 years getting two 3-microgram doses. The Covid vaccine is not yet authorised for use in children under the age of 5.
The United States Food and Drug Administration (FDA) earlier sought to fast-track Pfizer’s vaccine for infants and toddlers aged six months through 4 years old in response to the number of children hospitalised with Covid in the country.
However, the FDA and Pfizer decided to put those plans on hold after data on the first two doses did not meet expectations. The FDA is now waiting to see clinical trial data on a third dose for the youngest kids, which is expected in April.