Most COVID-19 Vaccine Boosters are Safe and Increase Immunity

The Lancet recently published a study that found six different COVID-19 boosters were safe and provoked strong immune responses in people who have previously received a two-dose primary vaccination course.

The COV-BOOST study looked at safety, immune response (immunogenicity), and side-effects (reactogenicity) of vaccines when used as a third booster jab.

Increases in anti-spike protein antibody levels after 28 days varied across the vaccines.

And all booster results were similar for participants aged 30-69 years and those aged 70 years or older.

Reactions to all vaccines were similar, with fatigue, headache, and injection site pain most often reported.

"The side effect data show all seven vaccines are safe to use as 3rd doses, with acceptable levels of inflammatory side effects like injection site pain, muscle soreness, fatigue. While all boosted spike protein immunogenicity after two doses of AstraZeneca, only AstraZeneca, Pfizer-BioNTech, Moderna, Novavax, Janssen, and Curevac did so after two doses of Pfizer-BioNTech", commented Professor Saul Faust on December 2, 2021, trial lead and Director of the NIHR Clinical Research Facility, University Hospital Southampton NHS Foundation Trust.

"It's encouraging that a wide range of vaccines, using different technologies, show benefits as a third dose."

"That gives confidence and flexibility in developing booster programs here in the UK and globally."

"It's important to note that these results relate only to these vaccines as boosters to the two primary vaccinations and to the immune response they drive at 28 days."

"Further work will generate data at three months and one year after people have received their boosters, which will provide insights into their impact on long-term protection and immunological memory."

"We are also studying two of the vaccines in people who had a later third dose after 7-8 months, although results will not be available until the new year," adds Professor Faust.

The authors warn that the boost ratios should be interpreted with caution because they relate to immunogenicity rather than protection against disease, and the relationship between antibody levels at day 28 and long-term protection and immunological memory is unknown.

The study has several limitations, such as due to pandemic timelines and the need to generate data to inform policy in September 2021, the interval between second and third doses was shorter in some participants than between their first two doses.

This study was funded by the UK Vaccine Taskforce and National Institute for Health Research.