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Alexandre_Nanchen
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Like their global counterparts, the two vaccines
authorised in India, Covaxin
and Covishield, while made
differently, were designed
on the blueprint of the virus
variant, called B1, that became the dominant strain in
India by last April.
With reports emerging
from vaccine trials, across
the globe, of certain mutations in the virus helping it
evade immune systems and
antibodies, several labs have
been working to check the
potency of vaccines against
emerging variants.
When the NIV scientists
tested the virus, bearing the
B.1.617 signature mutations,
on antibodies that were extracted from the blood serum of those with two doses
of Covaxin, they found
roughly 55% fewer antibodies than the antibodies
generated against B.1.
Similar study
When a similar study was
done with those inoculated
with Covishield, the Geometric Mean Titer (a proxy
for the number of antibodies) with B.1 was 42.92
whereas with the B.1.617 it
was 21.9, again roughly half.
On the other hand, when
antibody levels were compared against the B.1.1.7
(U.K. strain), there was only
a 6% reduction whereas
against Brazilian strain (P2)
there was again a 50% reduction. Dr. Samiran Panda,
who heads the Epidemiology Division at the ICMR, Delhi, and was a coauthor of
the papers, said while the
reductions were roughly on
these lines, they showed
that both Covishield and Covaxin were “almost similarly” protective against the
B.1.617.
In those vaccinated, protection against a future infection isn’t solely determined by the number of
antibodies and the extent to
which they wax and wane
over time, but also by the
mobilization of a class of defensive bodies called T cells,
which it is believed direct a
more specific kind of attack
against the virus and destroys it unlike antibodies,
which only block replicating
virus cells. “The antibody
tests don't account for the Tell response. Moreover
these tests were done on a
very small number of individuals. The average level of
antibodies don't always capture the true range of antibody production,” he told