* Laboratory study published on Pfizer vaccine
* Suggests local variant may reduce protective antibodies
* Real-world efficacy implications not yet clear
* South Africa expecting 7 mln Pfizer doses by June
* AstraZeneca jabs already on hold over trial data
* Country worst-affected by pandemic on continent
(Adds consultant comments, context)
By Alexander Winning and Wendell Roelf
JOHANNESBURG, Feb 18 (Reuters) - Scientists will meet on
Thursday to advise South Africa's government on its next steps
after a study suggested the dominant local coronavirus variant
may reduce protective antibodies from Pfizer's COVID-19 vaccine
by two-thirds.
The laboratory study, published in the New England Journal
of Medicine, is another worry for the country hardest-hit by the
pandemic on the African continent after it placed AstraZeneca
vaccinations on hold earlier this month.
Although its implications on the real-world efficacy of
Pfizer's vaccine are not yet clear, the study comes after
clinical trial data on the AstraZeneca, Johnson & Johnson
(J&J) and Novavax vaccines showed reduced
efficacy against the more contagious 501Y.V2 variant, first
identified late last year.
South Africa has been counting on the Pfizer shot,
developed with German partner BioNTech, to step up
its vaccination programme after administering the first J&J
doses on Wednesday.
It is considering swapping or selling its AstraZeneca doses,
after a small local trial, where participants were on average 31
years old, showed the vaccine offered minimal protection against
mild to moderate illness caused by the 501Y.V2 variant.
Officials are more confident about the J&J shot because it
was shown to be effective against severe illness in the local
leg of a large global trial.
The study published on Wednesday took into account all key
mutations of the 501Y.V2 variant. A paper published in late
January assessed the impact of only three key mutations of the
variant.
Scientists say that because the new study's findings come
from a laboratory, it is not easy to extrapolate what they might
mean in the real world.
Peter English, a consultant in communicable disease control,
said it was "far from proven" that the Pfizer vaccine would be
less effective against the 501Y.V2 variant. He said cellular
immunity - as well as antibodies - was important in protecting
against the virus and that scientists did not know the level of
neutralising antibodies needed for immunity.
"Our scientists will be meeting to discuss it (the study)
and they will advise the minister," health ministry spokesman
Popo Maja said.
Barry Schoub, chair of the Ministerial Advisory Committee on
vaccines, said the committee would discuss the study alongside
information on other vaccines.
Asked to comment on the findings, he said: "The Pfizer
vaccine is enormously effective at 95%, so even if there is
quite a significant reduction there still will be quite a bit of
remnant efficacy left.
"It is very likely that it will protect to a reasonable
extent, certainly against severe illness and mild to moderate to
some extent," he said.
"STRONG ENOUGH"
Richard Mihigo, an immunisation official at the World Health
Organization's Africa office, told a news conference the
antibody response to the variant in the Pfizer study was "strong
enough".
Linda-Gail Bekker, co-lead investigator of the South African
arm of J&J's global trial, said she would recommend rolling out
the Pfizer vaccine but monitoring it in the same way as the J&J
shot, which is being administered in an "implementation study"
targeting up to 500,000 health workers to further test it.
Health Minister Zweli Mkhize said on Wednesday South Africa
was expecting 500,000 doses of the Pfizer vaccine initially and
about 7 million doses by June.
A spokesman for regulator SAHPRA said Pfizer's registration
application was under review and declined further comment.
South Africa, with nearly 1.5 million cases and about 48,500
deaths, has recorded almost half the COVID-19 fatalities and
over a third of confirmed infections in Africa. It lagged richer
Western nations in launching its immunisation campaign.
The government plans to vaccinate 40 million people -
two-thirds of the population.
(Reporting by Alexander Winning in Johannesburg and Wendell
Roelf in Cape Town; Editing by Nick Macfie
Additional reporting by Kate Kelland in London, Ludwig Burger in
Frankfurt, Caroline Humer in New York and Aaron Ross in Dakar;
Editing by Olivia Kumwenda-Mtambo, Angus MacSwan, Raju
Gopalakrishnan and Timothy Heritage)