Six Different COVID-19 Boosters Effective for AstraZeneca or Pfizer-BioNTech Recipients

Recipients of either the Oxford-AstraZeneca (ChAdOx1-nCov19) or Pfizer-BioNTech (BNT162b2) COVID-19 vaccines can expect an immune response from one of several booster shots.

A randomized phase 2 trial of COVID-19 boosters found that 7 increase immunity when administered 10-12 weeks after 2 doses of the AstraZeneca vaccine, and 6 increase immunity after 2 doses of Pfizer-BioNTech.

“It’s really encouraging that a wide range of vaccines, using different technologies, show benefits as a third dose to either AstraZeneca or Pfizer-BioNTech. That gives confidence and flexibility in developing booster programs here in the UK and globally,” said Professor Saul Faust, who led the trial.

2 doses of AstraZeneca have shown to be 79% effective against hospitalization and death for at least 6 months, and 2 doses of Pfizer-BioNTech have proven 90% effective. However, with the outbreak of the Omicron variant, all fully vaccinated Americans are now advised to receive an additional “booster” dose.

The COV-BOOST study, published tonight in The Lancet, examine the immunogenicity and reactogenicity of 7 vaccines when administered as a third “booster” dose. The boosters studied were AstraZeneca, Pfizer-BioNTech, Novavax, Janssen, Moderna, Valneva, and Curevac.

The phase 2 trial included 2878 participants, all of whom were in good health at the time they were recruited from June 1-June 30, 2021. Participants came from 18 sites in the UK and received their first dose of either AstraZeneca or Pfizer-BioNTech in December 2020, January 2021, or February 2021.

After monitoring for adverse events, all 7 vaccines were declared safe to administer as a third dose. The most common side effects were injection site pain, muscle soreness, and fatigue; side effects were more frequently reported by participants 30-69 years of age. 912 of the 2878 participants reported 1036 adverse events, 24 of which were considered severe.

However, these boosters elicited varying antibody and cellular responses. While all 7 increased Spike protein immunogenicity after an initial regimen of AstraZeneca, all but AstraZeneca and Valneva boosted immune response among the Pfizer-BioNTech recipients.

After 28 days, participants initially vaccinated with AstraZeneca experienced anti-Spike protein antibody levels ranging from 1.8-32.3 times higher, dependent upon the booster administered. The participants vaccinated with 2 doses of Pfizer-BioNTech had antibody levels 1.3-11.5 times higher, according to the booster they received.

Looking forward, Faust said, “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.”