LONDON — A fourth dose of an mRNA vaccine significantly increases immune protection against the coronavirus at all ages, according to new research published Tuesday in the journal Lancet Infectious Diseases.

The study results will help immunization committees decide whether to expand booster programs to wider populations.

The researchers tested the cellular and antibody immune responses in people who had already received three doses of the BioNTech/Pfizer vaccine and in those who had received two doses of the Oxford/AstraZeneca vaccine plus a third BioNTech/Pfizer injection.

Half of the people in each group received another Pfizer vaccine, the rest received half of the Moderna booster dose, about 30 weeks after the third injection.

The results of the expanded COV-BOOST study revealed that those who received the Moderna injection had the most increased immunity with an approximately 16-fold increase from before the fourth injection.

Also, compared to 28 days after their third sting (when the immune response is highest), the Moderna booster on average has more than doubled the level of antibodies against the spike protein.

Reviews: -  recommended you read 4th COVID vaccine dose significantly boosts immunity, UK study finds

There was also a significant increase in immunity with a fourth dose of the BioNTech/Pfizer injection. Antibody levels increased an average of 12-fold compared to before the dose, and more than one and a half times compared to 28 days after the third injection.

The data also suggest a ceiling in antibody levels due to boosting with the two mRNA vaccines, the researchers found.

The findings come as countries continue to expand their retirement programs to older and more vulnerable groups, where reduced protection poses greater risks.

Although the European Medicines Agency has approved a fourth dose in vulnerable and immunosuppressed people, no vaccine has yet been authorized as a second booster in the general population.

Asked at a news conference Monday if the data supported the population increase, COV-BOOST principal investigator Saul Faust said the decision would be up to vaccination committees and based on infection rates. , hospitalizations and serious illnesses among those who received two and three doses. , as well as emerging variants.

He said current vaccines continue to protect people well against serious illness, even in people who received three doses of the AstraZeneca vaccine, which was found to generate lower levels of antibodies