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* Data behind UK booster decision published
* Pfizer and Moderna give large antibody, T-cell boosts
* Broad T-cell responses give hope of variant protection
(Adds reaction, additional study, TV media marker)
By Alistair Smout
LONDON, Dec 3 (Reuters) - COVID-19 vaccines made by Pfizer
and Moderna that use mRNA technology provide
the biggest boost to antibody levels when given 10-12 weeks
after the second dose, a new British study has found.
The "COV-Boost" study was cited by British officials when
they announced that Pfizer and Moderna were preferred for use in
the country's booster campaign, but the data has only been made
publicly available now.
The study found that six of the seven boosters examined
enhanced immunity after initial vaccination with
Pfizer-BioNTech's vaccine, while all seven increased
immunity when given after two doses of AstraZeneca's
vaccine.
"A third dose will be effective for many of the vaccines
we've tested and in many different combinations," Professor Saul
Faust, an immunologist at the University of Southampton and the
trial's lead, told reporters.
The study, published late on Thursday, found that a full
dose or half dose of Pfizer or a full dose of Moderna gave a
strong boost to both antibody and T-cell levels, regardless of
whether the person initially received Pfizer or AstraZeneca.
"All four of the vaccination regimes most widely deployed in
the UK lead to essentially the same levels of immunity and are
likely to be equally effective," said Professor Eleanor Riley,
immunologist at the University of Edinburgh. She added that a
policy change in booster gaps was also supported by the data.
"These data support the JCVI (vaccine committee) decision
earlier this week to bring forward booster doses to 3 months
after the second vaccination."
When AstraZeneca, Novavax, Johnson & Johnson and Curevac
were given as boosters, they increased antibody levels for
either initial vaccine, albeit to a smaller degree, the study
found. However, while Valneva boosted antibodies in people
initially vaccinated with AstraZeneca, it did not provide a
boost for Pfizer.
The COV-Boost study pre-dated the spread of the emergent
Omicron variant of concern, and Faust said he had shared samples
with the UK Health Security Agency to generate data on Omicron.
The study did however find that booster shots also helped to
generate a broad T-cell response against the Beta and Delta
variants, which may play a key role in longer-term protection.
A separate study by Imperial College London into how initial
exposure to SARS-CoV-2 shapes immune responses, also published
late on Thursday, similarly found a good T-cell response to both
Alpha and Delta after infection followed by vaccination.
(Reporting by Alistair Smout;
Editing by Bernadette Baum and Mark Heinrich)
