The findings of the not-yet-peer-reviewed and pre-print study,published on Monday,follow preliminary indications from early clinical trials that the vaccine fared poorly in children aged two to four,who received an even smaller dose.
In the study,six New York state public health scientists analysed outcomes for 852,384 fully vaccinated children aged 12 to 17 and 365,502 children aged five to 11 between December last year and January this year.
Vaccine effectiveness against infection in the older children decreased to 51 per cent from 66 per cent during the period,while in the younger children,it dropped sharply to just 12 per cent from 68 per cent.
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The Pfizer jab’s effectiveness was also significantly different between ages 11 and 12. The researchers found that at the end of January,the vaccine’s effectiveness against infection was 67 per cent in 12-year-olds,compared with just 11 per cent in 11-year-old children.
Australian infectious disease physicians and paediatricians still strongly recommend the Pfizer vaccine for children,arguing that despite a drop in protection against infection,the vaccine does its most crucial job:providing robust protection against severe disease.
University of Sydney infectious disease paediatrician and expert in vaccinology Robert Booy believed the sharp drop in Pfizer’s performance in young children may stem from the fact they receive one-third of the dose given to older children and adults.