I Got Vaccinated, Then I Got Covid. What Happened?
As good as even the most effective shots are, they can’t
promise total immunity. A Bloomberg Opinion editor found that out the hard way.
By Mary Duenwald and Sam Fazeli
March 5, 2021, 12:00 PM GMT Corrected March 5, 2021, 2:23 PM
GMT
Mary Duenwald, a Bloomberg Opinion editor, tested positive
for Covid-19 even after receiving both doses of the Pfizer Inc.-BioNTech SE
vaccine. Here, she discusses her experience with Sam Fazeli, a pharmaceutical
industry analyst for Bloomberg Intelligence. The conversation has been edited
and condensed.
MD: I was vaccinated
for Covid recently — I got my second Pfizer shot a
few weeks ago. I was hoping that meant I wouldn’t get Covid, yet I tested
positive this week. How is that possible?
SF: Thank you, Mary, for sharing your story. The reality is
that so-called sterilizing immunity,
or protection that completely blocks a virus from infecting you, is rare. In
fact, only one vaccine has been proven to provide that, and that is the
smallpox shot. If you think back to the phase III trials of the Pfizer-BioNTech
and Moderna Inc. vaccines — arguably the ones with the best efficacy so far
— they were 95% effective, meaning some
vaccinated people still developed symptoms after the second dose, even if at a
very low rate. Also, outside the environment of a clinical trial, efficacy
will be slightly lower; real-world data
is showing about 90% efficacy. It’s
also possible that you are infected with
a new variant, such as the one that is circulating in New York, known as
B.1.526. These variants are potentially better at getting past your antibody
immunity.
MD: My symptoms are
mild, as if this were just a cold. Can I assume the shot is still
protecting me?
SF: Of course. You will never know how bad your symptoms
would have been if you had not been vaccinated, but they could have been much
worse. The vaccines have high efficacy
against severe and critical disease — indeed their main purpose is to
keep people out of the hospital and lower their risk of dying. Even the
ones with apparently lower efficacy against mild and moderate disease, such as
Johnson & Johnson’s shot, show better efficacy against severe and critical
illness.
MD: Does being vaccinated mean I am less likely to transmit the virus to someone else?
SF: Some data suggest that is the case, but it is early
days. The antibodies generated by vaccination can stop a virus from actually
infecting you or from allowing the infection to “take.” Specifically, people
who are vaccinated and then test positive have lower amounts of virus in their
nasal passages and possibly even less in their lungs than if they were not
inoculated. This means there is less virus in the air you breathe out. How long
this lasts is not known, though. The data we have come from people soon after
their vaccinations, when they have high levels of antibodies. As the months pass, these levels
may fall to a level that they can’t stop an infection in the absence of a
vaccine booster or a natural infection like yours. We need to see the data on asymptomatic infections at six months and 12
months after the second dose of the vaccine to have a better idea.
MD: I
was tested the same day I learned I had been in contact with someone with
Covid, and again the next day, and both tests came back negative. The positive test came a week later.
Does that mean I wasn't infected by that person?
SF: No – there is an
incubation period that can last as long as two weeks. It’s possible that
people who are vaccinated have a longer incubation period as the virus is
hampered by the immune system. The other interesting question is whether
you need to quarantine as long as an unvaccinated person with an infection
does. Might you be safe sooner because you’ve had the vaccine? You might, but
we just don’t know yet.
MD: What’s the takeaway from my experience about how safe a
vaccinated person should feel, and the kind of measures they still need to
take, especially around the unvaccinated?
SF: Vaccinated people should feel safe until the data show
otherwise. Currently, very few people are showing severe infections after being
vaccinated, and that’s a good thing. At the same time, as long as there are
people out there who are not vaccinated, it is best to continue with masking
and distancing — for their sake.
MD: In a similar vein, some on the Bloomberg Opinion team
had questions about the risks involved with an elderly vaccinated person visiting unvaccinated relatives. Would
that be dangerous?
SF: The best answer is to wait until everyone in your
bubble is vaccinated. Then you can resume your normal behavior when
together.
MD: After I get through this, will I be immune to future
infections?
SF: It is possible that your infection has given you a
second “booster,” but I doubt anyone
will ever be 100% immune to mild infections. What would be interesting to
know is whether you are infected with one of the virus variants. If so, we
could then look at your immune response to see if it has changed and can give
you better immunity to this new variant the next time you encounter it. Sadly,
we don’t have a lab at Bloomberg to do this analysis.
(Corrects answer to first question about vaccine
effectiveness to not overstate the vulnerability of vaccinated people. )
This column does not necessarily reflect the opinion of the
editorial board or Bloomberg LP and its owners.
To contact the authors of this story:
Mary Duenwald at mduenwald@bloomberg.net
Sam Fazeli at mfazeli@bloomberg.net
To contact the editor responsible for this story:
Beth Williams at bewilliams@bloomberg.net
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