COVID-19 vaccine boosters give well-maintained immunity three months on

Receiving a third dose of a Covid-19 vaccine approved in the UK offers a prolonged immune response, a study at UCLH has found.

The COV-BOOST study compared the immune response from seven* vaccines given as a third dose to people who had received two initial doses of either the AstraZeneca or Pfizer vaccines.

The latest findings from the study, published online in the Journal of Infection, reveal strong immune responses 84 days after third doses with the five vaccines currently approved for use in the UK (AstraZeneca, Pfizer, Moderna, Janssen and Novavax vaccines). Three of these (Pfizer, Moderna and AstraZeneca) have been used in the UK booster programme.

Of the 2,883 participants involved in the study (all aged over 30), 2,422 had no Covid-19 infection in the period through to their three-month visit.

In those who had two initial doses of AstraZeneca, the Pfizer and Moderna mRNA vaccines given as a third dose gave the highest anti-spike antibodies at day 84.

In people who had two initial doses of Pfizer there was no significant difference at day 84 between those given a third jab of AstraZeneca or Pfizer. Those given Janssen’s jab as a third dose after two doses of Pfizer showed an even stronger anti-spike antibody response at day 84.

Responses to a half or full dose of Pfizer were similar in both those who had AstraZeneca or Pfizer initial doses.

Importantly, the rate that immune cell responses declined after third doses was similar between all the vaccine combinations and doses.

Professor Vincenzo Libri, who led the trial at UCLH, said: “It was great that our Trust supported recruitment of this vital study, the findings of which give really important information on which vaccines still offer a strong immune response three months after a third jab vaccination. We thank all the participants who took part.”

*The seven vaccines trialled were:

  • AstraZeneca (Oxford-AstraZeneca)
  • Pfizer (Pfizer-BioNTech)
  • Moderna
  • Novavax
  • Valneva
  • Janssen
  • CureVac (first-generation vaccine no longer in clinical development)