December 11, 2020 BY MD ANDERSON STAFF
As the number of COVID-19 cases continues to increase, you
probably have a lot of questions about the coronavirus vaccine. Why are health
care workers receiving the COVID-19 vaccine first? How soon will you be able to
get the COVID-19 vaccine and get back to some semblance of a normal life? When
can cancer patients get vaccinated?
For answers, we spoke with our chief medical
officer Welela Tereffe, M.D., and infectious diseases
specialist and head of Internal Medicine David Tweardy, M.D.
Why are health care workers receiving
the COVID-19 vaccine before patients?
Tereffe: As vaccine production ramps up,
there will be a limited number of doses available.
Federal and state guidelines require that, as long as
vaccine supply is limited, the vaccine must be available to health care workers
first. MD Anderson is one of the Houston health systems selected as a
pre-position site for COVID-19 vaccines that are authorized by the Food and
Drug Administration for emergency use. MD Anderson’s initial vaccination
clinics will safely and efficiently vaccinate health care workers caring for
highly immune compromised patients and those with increased risk of
occupational exposure.
By offering the vaccine to health care workers first,
public health officials hope to reduce everyone’s risk – patients and staff –
of exposure to the coronavirus in hospitals and clinics and to ensure continued
care for patients.
When will the COVID-19 vaccine be
available for cancer patients?
Tereffe: People with serious health
conditions such as cancer, and people with weakened immune systems, were not
included in many of the COVID-19 vaccine clinical trials.
As the vaccine becomes more widely available, we’ll
learn more about the indications, benefits, and side effects in people with
serious health conditions. Your care team will then be able to give you that
information so you can make an informed choice about vaccination.
It’s important to continue taking precautions such as
wearing a mask, maintaining social distancing and washing your hands
frequently, even after you receive a COVID-19 vaccine. These precautions will
be necessary until public health experts advise otherwise.
How do the Pfizer and Moderna vaccines
work?
Tweardy: Our cells use messenger RNA
(mRNA) to produce the various proteins our bodies need to function. The Pfizer
and Moderna vaccines both use an mRNA sequence that codes for the unique spike
protein on the surface of the SARS-CoV-2 virus. Once a person receives the
vaccine, their cells take up that mRNA sequence and produce the COVID-19 spike
protein. Their immune system then detects those proteins as foreign and creates
antibodies against them, which helps provide protection from future COVID-19
infections.
Currently, both of these vaccines require two doses
given a few weeks apart to be effective.
What are the other types of
coronavirus vaccines being developed?
Tweardy: There are three other types
being developed that are in the lead. One involves deactivated virus. The third
type uses a carrier virus (such as an adenovirus) containing the part of the
coronavirus’ DNA that encodes the spike protein. The fourth type uses a single
protein from the tip of the spikes that cover the coronavirus and allow it to
bind to and infect human cells.
The type that uses deactivated virus is the most
old-fashioned and the least sophisticated. It involves injecting people with
virus that’s been inactivated (or made harmless) through heat or some other
means. This causes a very broad immune response in the recipient, but not
necessarily the one you want.
The carrier virus method targets the really important
part of the virus — the protein spikes that stick up like little maces all over
its surface — instead of the virus as a whole. It prompts the body to generate
the spike protein itself. Once that happens, the immune system recognizes it as
an invader and starts developing antibodies against it. So, when the real
coronavirus comes along, these antibodies can shut it down. This is the
strategy that most of the vaccine makers are pursuing right now.
The last type of coronavirus vaccine involves injecting
people with the spike protein itself, instead of pushing their bodies to
generate it.
All three of these last approaches have been used
successfully, based on the studies done so far. The last one is just not quite
as far along in testing as the RNA and carrier approaches are.
What makes the RNA-approach so
different from that of previous vaccines?
Tweardy: This is the first time this type
of technology has ever been used for a vaccine. And the speed at which it is
being developed is truly mind-boggling.
Remember, this particular coronavirus was virtually
unknown in November 2019. The actual syndrome caused by it was only first
described in December 2019. A month later, scientists had isolated the virus
and sequenced its genome. That’s something that used to take a full year or
more. Two months later, we had the first COVID-19 vaccine candidates. Four
months after that, some were already in Phase III clinical trials. And we’ll
have a coronavirus vaccine available to health care workers in December 2020.
We’re living through a modern scientific miracle.
Vaccines have not been developed at this speed before. Vaccine development
usually takes 10 to 15 years after the identification of a new infectious
disease. I’ve been working in infectious diseases for 40 years, and I never
would’ve thought it was possible.
Could this same mRNA vaccination
method be used again against future coronaviruses?
Tweardy: Absolutely. This strategy has
the capacity to almost let us anticipate the next strain of
coronavirus so we can be prepared for it, kind of like we do now with the flu.
We could sequence the next coronavirus that’s identified
as distinct and separate from this one in a month or less. Once we had that, we
could insert the sequence of its spike protein into every step of the vaccine
development pathway. That could get us another vaccine for testing within three
months.
With this family of coronaviruses, that could
potentially allow us to have a vaccine ready before the next one even becomes a
pandemic. So theoretically, we could stop the next pandemic in its tracks.
Is the coronavirus vaccine safe?
Tweardy: Yes. I think anyone who gets a
coronavirus vaccine can have confidence that it will be safe. Otherwise, it
wouldn’t be approved. The Food and Drug Administration has been looking at this
very carefully, and the vaccine has had to be tested on a lot of people to get
approved.
COVID-19 is caused by a coronavirus similar to SARS and
MERS, and researchers were able to build upon previous work creating vaccines
for these diseases as they searched for a vaccine against COVID-19. mRNA has
been studied for many years in relation to the study of infectious diseases and
as an area of opportunity in cancer treatment.
COVID-19 is the third in a series of coronaviruses.
After SARS and MERS, we understand the pathogenesis and early aspects of
immunity and have learned from those experiences and taken that knowledge to
target the weak spot of coronaviruses.
Even more closely watched than the efficacy of the
vaccines in the clinical trials is the safety of the participants. For the FDA
to consider an application for emergency authorization of a vaccine, more than
half of the people enrolled must have been monitored for at least two months.
Preliminary data shows the observed side effects are very similar to the flu
vaccine, such as pain at the injection site and fatigue.
The FDA’s vaccine advisory committee comprises experts
in medicine and research who meet to review the request for emergency use
authorization (EUA) of the vaccine, and these experts evaluate the safety and
efficacy of the vaccines. Clinical trial participants will continue to be
followed even after any EUAs are granted.
Should I be concerned when I hear that an ongoing COVID-19 vaccine trial has
been paused?
Tweardy: No. It’s fairly common for
studies to be stopped temporarily. This gives researchers time to determine if
any serious adverse events people experience are due to the vaccine or caused
by something else.
Even during a pandemic, life goes on, so people can
still become ill for any number of reasons. If researchers determine the
adverse events are unrelated to a vaccine, then studies can be restarted. This
has occurred in the case of two big COVID-19 vaccine trial; the pause was
lifted and the trial restarted after a one-week review by independent trial
safety experts determined that the adverse event was unrelated to the vaccine.
How long will the coronavirus vaccine
be effective?
Tweardy: We’d obviously love for it to
give lifelong immunity against COVID-19, but that remains to be seen. If I had
to guess, I would say it’s probably going to fall somewhere between influenza
and the mumps, in terms of longevity of protection. It will probably be closer
to the flu, because respiratory viruses don’t tend to lead to long-term
immunity.
Related stories
·
Insights from a COVID-19 vaccine
clinical trial participant
·
When will we achieve herd immunity?
·
What counts as COVID-19 exposure?
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