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Study run in Oxford publishes COVID-19 booster data

03/12/2021

Six COVID-19 vaccines are safe and boost immunity for people who have had two doses of AstraZeneca or Pfizer-BioNTech, results from the UK-wide COV-BOOST trial show.

The world-first study, which recruited volunteers at the Oxford Vaccine Group at the Churchill Hospital, was key to shaping the UK booster programme and gives vital evidence for global vaccination efforts. 

The study, led by University Hospital Southampton, had its latest results published in the Lancet.

COV-BOOST looked at the safety, immune responses and side-effects of seven vaccines when used as a third, booster jab. A total 187 volunteers joined the study in Oxford.

Run at 18 National Institute for Health Research (NIHR)-supported sites, the study saw 2,878 people aged 30 or over recruited. Participants received one of these boosters 10-12 weeks after their initial two-dose vaccination with either AstraZeneca or Pfizer-BioNTech. A control group was given a meningitis vaccine, to account for reactions not specific to the COVID-19 jabs.

The seven vaccines trialled were: Oxford-AstraZeneca, Pfizer-BioNTech, Moderna, Novavax, Valneva, Janssen, CureVac. Of these, only AstraZeneca, Pfizer-BioNTech, Moderna and Janssen are currently licensed for use in the UK.

Dr Angela Minassian, Senior Clinical Researcher at the Oxford Vaccine Group and Principal Investigator in Oxford for the COV BOOST trial, said: "This study has, for the first time, demonstrated the ability of a wide range of vaccines to safely and effectively boost pre-existing immune responses induced by the AstraZeneca and Pfizer vaccines. 

"More follow-up data is required to confirm the durability of these boosted responses and whether this translates into longer-term protection from COVID-19 disease. However, the current data are hugely encouraging and also support using lower doses of vaccines, particularly of the mRNA vaccines, as boosters. This is good news for preserving vaccine supply in addition to allowing flexibility of schedules as countries develop their booster campaigns."

Professor Saul Faust, trial lead and Director of the NIHR Clinical Research Facility, University Hospital Southampton NHS Foundation Trust, said: "Our side effect data shows all seven vaccines are safe to use as a third dose, with acceptable levels of 'reactogenicity' - inflammatory side effects like injection site pain, muscle soreness, fatigue. All seven boosted levels of spike protein antibodies significantly after two doses of AstraZeneca. However only six also did so after two doses of Pfizer-BioNTech (AstraZeneca, Pfizer-BioNTech, Moderna, Novavax, Janssen and CureVac). There were also large variations in response with different boosters.

"It's really encouraging that a wide range of vaccines, using different technologies, show benefits as a booster dose to either of these vaccines. That gives confidence and flexibility in developing booster programmes here and globally, with other factors like supply chain and logistics also in play."

There were large differences in spike protein antibody levels after 28 days across the vaccines. In people who had received two initial doses of AstraZeneca, these ranged from 1.8 times higher to 32.3 times higher with different booster vaccines. For those who had received Pfizer-BioNTech initially, the range was 1.3 times higher to 11.5 times higher. Booster results were similar for those aged 30-69 years and those aged 70 years or older.

The study also looked at immune T-cell responses. T-cells are likely to be important in controlling disease severity, although their impact on overall protection or longevity of immunity is not yet known. COV-BOOST reported T-cell responses in several combinations of initial and booster vaccines, however these were not predictable based on spike protein antibody levels.

Reactions to all seven vaccines were similar, with fatigue, headache, and injection site pain most often reported. These were more commonly reported by those aged 30-69. 

Prof Faust added: "It's important to note two things about these results. First, they only relate to these vaccines as boosters to the two primary vaccinations, not how well they work as first and second doses. Secondly, the data describe the immune response at 28 days, not vaccine effectiveness. The relationship between that response and long-term protection is still poorly understood. We will be looking at the longer-term immune responses in COV-BOOST, conducting further tests at three months and one year after receiving boosters."

Professor Andrew Ustianowski, National Clinical Lead for the UK NIHR COVID Vaccine Research Programme, said: "Heading into the winter, and due to the emergence of the Omicron variant, the results from the COV-BOOST study are extremely timely and of national and international importance.

"Since the beginning of the pandemic the NIHR and the NHS have been supported by the efforts and selflessness of study participants - helping us to identify the most effective vaccines and how they can be used flexibly to protect more people.

COV-BOOST was designed so that stored samples can be used in evaluating these vaccines’ effectiveness in neutralising any new variants of concern, and COV-BOOST samples have been made available to the UK Health Security Agency for testing against Omicron.

Image credit: CDC via Unsplash