On Friday (17 December), vaccine maker Pfizer said its trials for the vaccine in children aged 2 to 5 showed that it did not provide the expected immunity in kids this age, and it is adding a third dose to the regimen.
In a statement, Pfizer said the companies tested 3 micrograms of the vaccine (one-tenth of the adult doses) in children aged 6-months to less than 5-year-old.
After two doses, children between 6-months and 2-year-old produced an immune response that was comparable to that of people aged 16 to 25 years, but children between 2 and 5-year-old did not.
In a conference call with investors and analysts, Pfizer’s head of vaccine research, Dr Kathrin Jansen said the company now plans to seek authorisation for a “three-dose series” in children, instead of the originally planned two doses.
She added that if this revised strategy works, the company will have a consistent three-dose vaccine approach for all ages.
Meanwhile, the announcement once again give emphasis on the idea that people should only be considered “fully vaccinated” after receiving what are now viewed as booster shots.
Early studies indicate that 3 doses of the mRNA vaccines may provide a stronger protection against the Omicron variant than 2 doses.
Meanwhile, Pfizer also said they will seek the authorisation from Food and Drug Administration (FDA) and the European Medicines Agency for a three-dose series in younger children in the first half of 2022.
The FDA has on last week authorised booster shots of the Pfizer-BioNTech vaccine for adolescents ages 16 to 17.
Nonetheless, Pfizer did not provide an update on when it planned to ask the agency to authorise booster shots for children five to 15 years of age.
The FDA has previously authorised the full adult dose for immunisations of adolescents 12 through 17 years of age.
The companies plan to test booster doses of 10 or 30 micrograms to assess the safety and potency of both doses in 600 children in that age group.
The mRNA vaccines have been linked in some rare cases to heart problems in boys and young men, prompting some experts to suggest a lower dose for adolescents.