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COVID-19 vaccine boosters give well-maintained immunity three months on, finds study ran in Yorkshire & Humber.

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The latest results from the COV-BOOST study, which ran at Bradford Royal Infirmary and St James’ University Hospital,, have shown prolonged immune responses following third doses of several COVID-19 vaccines.

Run at 18 NIHR-supported sites across the UK, the study led by University Hospital Southampton provided the world’s first data on the safety and immunogenicity of a third dose in mix and match schedules, underpinning the UK’s autumn 2021 booster roll-out.

Over 400 participants took part in the study in Yorkshire & Humber.

It compared the immune response from seven vaccines, 28 days after administration as a third dose in people who had received two initial doses of either AstraZeneca or Pfizer.

The latest findings, published online in the Journal of Infection, reveal strong immune responses are still seen 84 days after third jabs with five of the COVID-19 vaccines currently approved for use in the UK (AstraZeneca, Pfizer, Moderna, Janssen and Novavax vaccines). Of these vaccines, only three (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 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.

However, 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.

The seven vaccines trialled in the main COV-BOOST trial were:

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

Ongoing COV-BOOST sub-studies are investigating the interval between second and third doses, fourth doses of mRNA vaccines, an Omicron variant vaccine and fractional dosing in young people aged 18-30 years.