UK-wide COVID-19 vaccine study reports long-term third dose booster protection

Third dose COVID-19 booster vaccines offer lasting protection after several months, according to the latest results of a nationwide trial which at UCLH took place at the NIHR UCLH Clinical Research Facility (CRF) with the support of the UCLH BRC.

The COV-BOOST study, led by University Hospital Southampton, has provided data to underpin the UK’s booster programmes since 2021.

New analysis, published online in the Journal of Infection, is reporting immune responses eight months after third doses of several COVID-19 vaccines.

The insight could be important around the globe if longer-term protection becomes a higher priority when choosing vaccines for booster programmes.

Researchers found adenovirus-based vaccines (such as those from Janssen or Oxford-AstraZeneca) may lead to similar immune responses as mRNA vaccines (such as the Moderna or Pfizer-BioNTech vaccines) at around seven months after the third dose of vaccine. They also report that lower doses of mRNA vaccines may offer lasting protection as boosters.

Booster study

COV-BOOST, which at the NIHR UCLH CRF was led by Principal Investigator Professor Vincenzo Libri, provided the world’s first data on the safety and immunogenicity of a third dose in mix and match schedules.

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

Last year, the study reported strong immune responses were seen 84 days after third jabs in several approved COVID-19 vaccines.

A fourth dose sub-study also found that an mRNA vaccine is safe and boosts antibody levels - even higher than that of a third dose.

UK-wide research effort

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)

The trial initially included ten experimental vaccine arms (seven full-dose, three half-dose) delivered at three groups of six sites.

The latest report analyses the responses to third doses of the original (wild type) vaccines from 817 participants in seven study arms.

The current mRNA vaccines recommended by the Joint Committee on Vaccination and Immunisation (JCVI) are bivalent vaccines that have been upgraded to target two circulating variants of COVID-19. This study used wild-type mRNA vaccines that targeted the original strain of COVID-19 and therefore cannot be directly compared to the vaccines used in more recent campaigns.

Image credit: Rido via Adobe Stock