[ 2021-02-04 ]

Here's why some people test positive after getting a Covid-19 vaccine

A Covid-19 vaccine does not provide full or
immediate protection, which means it's still
possible to get infected and test positive for the
virus.

Democratic Rep. Stephen Lynch of Massachusetts
did. He tested positive after he got his second
dose of the Pfizer vaccine. Hall of Fame
basketball coach Rick Pitino, who coaches the
men's team at Iona College in New York, also
tested positive after getting his first dose.

They could have tested positive for a few
reasons.

There's a lag between vaccination and protection

It takes a few days to a few weeks for the vaccine
to work, according to the US Centres for Disease
Control and Prevention. You could test positive
before the vaccine kicked in.

"It takes a while for the immune response to
develop," said Dr. Robert Salata, director of
University Hospitals Roe Green Centre for Travel
Medicine & Global Health in Cleveland.

The first dose may provide some protection, but as
the Moderna CEO, Stephane Bancel said Monday "but
we really just don't have any data to prove that
at this point."

For Pfizer, after 14 days the first dose was
around 52% effective at preventing disease,
Salata, who was the lead investigator for the
Pfizer vaccine at his hospital, said.

Vaccination prevents most, but not all disease
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You could still test positive after being
vaccinated since the vaccine is not 100%
effective.

The two US-authorized vaccines are highly
effective but they don't provide total
protection.

The Pfizer vaccine was 95% effective at preventing
illness in clinical trials after people got two
doses.

The Moderna vaccine was 94% effective at
preventing illness in people who got two doses in
clinical trials.

Vaccination prevents disease, but infection, it's
unclear

Vaccination prevents disease, but it's still
unclear if, or how much, the vaccine prevents all
infections.

"The information is less clear whether the
vaccines will prevent the virus from infecting us
and we can remain without symptoms. That's still
under study." said Dr. William Schaffner, an
infectious disease specialist and a professor of
preventive medicine in the Department of Health
Policy at Vanderbilt University.

"As far as what we've seen, these vaccines are
really game changing at preventing disease and
even severity of disease," said Namandje Bumpus,
director of the department of pharmacology and
molecular sciences at Johns Hopkins University.

"But focusing on the efficacy number doesn't paint
the whole picture, because you could still end up
with Covid, but by all indications that appears
that those cases are still really less severe than
unvaccinated people and that's really important."

The vaccine makers are still studying if the
vaccines just keep people from getting really sick
or if they totally protect from infection.

If you are asymptomatic you would still test
positive for Covid-19. That would also mean even
if you are vaccinated you could also still spread
the disease. That's why even the vaccinated will
still need to wear masks. A person could be an
asymptomatic carrier and have the virus in their
nasal passageways, so when they are breathing or
speaking or sneezing they could still pass the
novel coronavirus on to others.

Vaccines don't work retroactively

Vaccines don't work retroactively. You could test
positive because you were infected before you got
the vaccine and just did not know it yet. That's
what happened to some of the health care workers
in a study published by the US Centers for Disease
Control and Prevention Monday.

The study found that 22 of 4,081 vaccinated health
care workers tested positive for Covid-19 after
getting their first dose.

One of the study authors, Dr. Eyal Leshem of Sheba
Medical Center in Israel, said it was clear that
some of the workers that tested positive "were
actually infected with Covid before they get their
first dose."

The variant question

There's concern that certain variants that have
been spreading in the US could be less susceptible
to the protection that comes from vaccines.

Preliminary lab data shows the vaccines should
provide protection, and public health leaders want
to get as many people vaccinated as quickly as
possible to limit the opportunities the virus has
to mutate.

The Covid-19 vaccine makers said they are testing
to see if the vaccines work against the variants
and they're also working on boosters that would
add extra protection against variants.

"It is possible a year from now, that I'll get a
flu shot in one arm and a Covid vaccine update
booster in the other," Schaffner said. "We'll have
to adapt ourselves to what it is that this virus
is doing. And we have the capacity to keep up with
the virus, and even get ahead of it."

Source - CNN

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