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(Adds scientists' quotes, details, background)
By Kate Kelland
LONDON, April 14 (Reuters) - The first study to directly
compare immune reactions between Pfizer's and AstraZeneca's
COVID-19 vaccines found strong and broadly similar antibody
responses in over 80-year-olds after a first dose of either
shot, scientists said on Wednesday.
The UK study also found that a critical component of the
immune system known as T cells showed a more enhanced response
in those who got the AstraZeneca/Oxford University
vaccine than in those who got the Pfizer/BioNTech
one.
The scientists behind the study, which analysed blood
samples from 165 people in Britain aged between 80 and 99 who
had been given a first COVID-19 vaccine dose, said that finding
merited further investigation.
While antibodies can block the coronavirus' ability to enter
human cells, T cells can act as broader protection by attacking
and killing any cells that have been infected with the virus.
"These vaccines are both equivalent and effective at
inducing antibody responses in the great majority of people (in
this study), even after one dose," said Paul Moss, a professor
of haematology at Britain's Birmingham University who co-led the
research.
"Both vaccines are good," he told a briefing on the
findings.
The study was published online as a preprint before being
peer reviewed. It found that key antibodies were present and at
similar levels in 93% of the 76 study participants who got the
Pfizer single COVID-19 vaccine dose, and 87% of the 89
participants who got the AstraZeneca shot.
Helen Parry, clinical lecturer at Birmingham University who
co-led the study, said the tests also showed that a larger
proportion of those who got the AstraZeneca vaccine had a
detectable T cell response.
That finding adds to other emerging evidence from COVID-19
studies suggesting that antibodies - which stop the coronavirus
from being able to attach to human cells - may not be the only
important element of immunity, and that T-cells may also have an
important protective role.
"We now need to carry out further research to understand
what this difference in T cell responses means," said Parry.
Around half of the UK population have had at least one dose
of a COVID-19 vaccine, one of the highest rates of inoculation
in the world. The vast majority have received either the Pfizer
or the AstraZeneca shot.
(Reporting by Kate Kelland, ; editing by John Stonestreet)
