New data suggest the Pfizer-BioNTech COVID vaccine works substantially less well at preventing infection and hospitalisations in children aged 5 to 11 than it does in those aged 12 to 17, raising questions about whether the companies chose the wrong dose for the younger children, reports STAT News.
The data show a rapid decline in protection after vaccination in children in the younger age group, with efficacy against infections dropping off more quickly and dramatically than the declines seen in children aged 12 to 17. The study also found a significant decline in protection against hospitalisations.
The findings, compiled by researchers working for the New York State Department of Health, were posted this past Monday (28 February) on a preprint server: the study has not yet been peer-reviewed.
The New York findings, along with data from several other databases, were recently presented to the COVID vaccine work group of the Advisory Committee on Immunization Practices, independent vaccine experts who advise the Centers for Disease Control and Prevention (CDC), sources told STAT.
The information comes on the heels of disappointing results from Pfizer trials of an even lower vaccine dose in children under the age of 5. And they will raise questions about whether in trying to find doses that were both protective and tolerable in children, the companies failed to hit the mark for both age groups.
Pfizer would not say if it is exploring the possibility that the dose used in children might be too low, but said it is “confident in the protection and safety” of its COVID-19 vaccine.
“Our updates earlier this year on pursuing a three-dose schedule for the paediatric population were informed by the effectiveness data for three doses of the vaccine for people 16 and older, and the early laboratory data observed with Delta and other variants of concern, including Omicron, which suggest that people vaccinated with three doses of a COVID-19 vaccine may have a higher degree of protection,” it said in a statement.
But John Moore, a virologist at Weill Cornell Medical College said it was hard to see how the lower efficacy in 5 to 11-year-olds could be due to anything but the lower dose they received. In the study, children aged 12 had the highest vaccine efficacy of all age groups in both cohorts.
“The striking difference between 11-and 12-year-olds can only be explained by the three-fold dosing reduction in the younger children. The one-year age difference is highly unlikely to make any other factor relevant,” Moore said. “The 11-year-olds got the three-fold reduced dose, the 12-year-olds the standard dose.”
The New York study analysed health records for COVID cases in children and teens from 13 December 2021 to 30 January 2022, while the Omicron variant was replacing all other forms of the virus. COVID vaccines are not as protective against Omicron as they were against earlier versions of the virus, especially without a booster shot.
The state recorded more than 850,000 COVID cases in adolescents aged 12 to 17 during that time, and about 365,000 in children aged 5 to 11.
Over that period, two-dose vaccine protection against infection for 5 to 11-year-olds declined from 68% to 12%; the jab’s effectiveness at preventing hospitalisation declined from 100% to 48%.
But two-dose protection against infection for children aged 12 to 17 only dropped from 66% to 51%, and protection against hospitalisation from 85% to 73%, reports Stat News.
“Our data support vaccine protection against severe disease among children 5-11 years, but suggest rapid loss of protection against infection, in the Omicron variant era,” the researchers wrote. “Should such findings be replicated in other settings, review of the dosing schedule for children 5-11 years appears prudent.”
The adult Pfizer regimen, used in anyone aged 12 and older, is two doses of 30 micrograms apiece, given 21 days apart. Children 5 to 11 years old receive a dose that is one-third that size, two doses of 10 micrograms apiece. And in studies of children under 5, the dose is further reduced, with the children aged 6 months to 4 years getting two 3 microgram doses. The vaccine is not yet authorised for use in children under 5.
In December, Pfizer announced that two doses of the vaccine in children under 5 had not generated the same level of antibodies as was seen after two doses in people 16 to 25, which was being used as a proxy for protection. It said it would give the children under 5 a third dose to see if that achieved the required level of protection.
But then as Omicron cases spiked, the Food and Drug Administration (FDA) revealed it was considering authorisation for the vaccine for children under age 5, allowing parents to start vaccinating their children while waiting for the third dose. The rationale was that the risk-benefit equation had shifted with Omicron.
A meeting of the FDAʼs vaccine advisers, the Vaccines and Related Biological Products Advisory Committee, was scheduled for mid-February. But before the group could meet the FDA and Pfizer announced the plan was on hold. The plan is now to wait for the third-dose results before considering authorisation in this age group.
Study details
Effectiveness of the BNT162b2 vaccine among children 5-11 and 12-17 years in New York after the Emergence of the Omicron Variant
Vajeera Dorabawila, Dina Hoefer, Ursula E Bauer, Mary Bassett, Emily Lutterloh, Eli Rosenberg
Pre-print published on
Abstract
Importance
There is limited evidence on the effectiveness of the BNT162b2 vaccine for children, particularly those 5-11 years and after the Omicron variant’s emergence.
Objective
To estimate BNT162b2 vaccine effectiveness against COVID cases and hospitalisations among children 5-11 years and 12-17 years during December, 2021 and January, 2022.
Design
Analyses of cohorts constructed from linked statewide immunization, laboratory testing, and hospitalisation databases.
Setting/Participants
New York State children 5-17 years.
Main outcomes/measures
New laboratory-confirmed COVID-19 cases and hospitalisations. Comparisons were made using the incidence rate ratio (IRR), comparing outcomes by vaccination status, and estimated vaccine effectiveness (VE: 1-[1/IRR]).
Results
From December 13, 2021 to January 30, 2022, among 852,384 fully-vaccinated children 12-17 years and 365,502 children 5-11 years, VE against cases declined from 66% (95% CI: 64%, 67%) to 51% (95% CI: 48%, 54%) for those 12-17 years and from 68% (95% CI: 63%, 72%) to 12% (95% CI: 6%, 16%) for those 5-11 years. During the January 24-30 week, VE for children 11 years was 11% (95%CI -3%, 23%) and for those age 12 was 67% (95% CI: 62%, 71%). VE against hospitalisation declined changed from 85% (95% CI: 63%, 95%) to 73% (95% CI: 53%, 87%) for children 12-17 years, and from 100% (95% CI: -189%, 100%) to 48% (95% CI: -12%, 75%) for those 5-11 years.
Among children newly fully-vaccinated December 13, 2021 to January 2, 2022, VE against cases within two weeks of full vaccination for children 12-17 years was 76% (95% CI: 71%, 81%) and by 28-34 days it was 56% (95% CI: 43%, 63%). For children 5-11, VE against cases declined from 65% (95% CI: 62%, 68%) to 12% (95% CI: 8%, 16%) by 28-34 days.
Conclusions and Relevance
In the Omicron era, the effectiveness against cases of BNT162b2 declined rapidly for children, particularly those 5-11 years. However, vaccination of children 5-11 years was protective against severe disease and is recommended. These results highlight the potential need to study alternative vaccine dosing for children and the continued importance layered protections, including mask wearing, to prevent infection and transmission.
See more from MedicalBrief archives:
FDA committee endorses Pfizer-BioNTech vaccine for 5- to 11-year-olds
Pfizer vaccination ‘highly effective’ against Delta in adolescents — Israel study
Moderna interim results show that its low-dose vaccine works for 6-11-year-olds
Healthy boys at greater risk from vaccination than COVID itself — US analysis