A
sequel to a movie that you didn’t want to see in the first place is one thing,
like Ghost Rider 2 after Ghost Rider. A sequel to
having a COVID-19 infection would be something completely different.
You may
think that the one “positive” of testing positive for the
COVID-19 causing coronavirus (SARS-CoV2) and surviving would be that you won’t
get infected by that virus again. At least not during this pandemic. Ah, but is
this assumption really true? Will you indeed be immune to the SARS-CoV2 after
you’ve recovered from a COVID-19 infection? Some reports out of Japan and China
seem to suggest otherwise.
For
example, Daniel Leussink and Rocky Swift reported for Reuters about
a female tour bus guide in Japan who tested positive for the virus after
recovering from a COVID-19 infection. Here is a UNTV news
report on the case:
Does
this case actually prove that re-infection with the virus is possible? Or was
this just a mistake in the testing? Or did the person have a particularly weak
immune system so that she couldn’t generate immunity? After all, one case can
be an accident, an aberration, an anomaly, an aardvark in a sea of anemone.
Well,
oops something like this happened again, according to a more recent NHK-World Japan report. This
time it was a man in his 70’s, who first tested positive for SARS-CoV2 on
February 14 while on a Diamond Princess cruise ship. After being transferred to
a medical facility in Tokyo, he stayed there until testing negative for the
virus. On March 2, he left the facility and traveled home via public
transportation. However, the man eventually began feeling sick with a fever,
which prompted him to go to a hospital on March 13. The following day he tested
positive for the virus again.
Then
there’s the February 14 article from Caixin, a
Beijing, China-based media group, that was entitled “14% of Recovered Covid-19
Patients in Guangdong Tested Positive Again.” Umm, 14% would seem more like an
“ooop” than an “ooops.” This CGTN news warned of such
reinfection possibilities:
Remember
though, these are news reports and not scientific studies yet. While the
reappearance of Nicholas Cage with a flaming skull riding a motorcycle may not
call for additional scientific studies, all of these cases certainly do. First,
scientists need to confirm whether the test results were indeed accurate.
Remember, no test is perfect. If people can screw up a drink order, they can
certainly mess up a medical test. Even if a test is performed properly, you
could still get a positive result when you don’t actually have an infection. On
the flip side, just because you test negative doesn’t necessarily mean that
there is no way that you are carrying the virus. That’s why a doctor may test
you multiple times to be sure of a result.
Secondly,
doctors and other scientists need to double-check or triple-check that each of
these patients actually got re-infected with the virus rather than had an
infection that simply lasted a long time. What if, for example, the cruise
passenger and the tour bus guide each had fairly long infections and just
happened to have intervening false negative test results? The tests could have
simply been like commercial breaks in the middle of a single long episode of a
television show.
Third
of all, the amount of immunity that you build up after being exposed to any
virus depends on not only virus itself but surprise, surprise your immune
system and its response. When your immune system sees a particular virus for
the first time, it can essentially get caught with its pants down, not ready to
defend your body against this new invader. However, exposure to the virus
either through a vaccine or getting infected may train your immune system so
that, borrowing the words of former President George W. Bush, “fool me once,
shame on — shame on you. Fool me — you can't get fooled again.” If strong
enough, your immune system then may be ready with proper defenses next time the
virus comes calling. Could the cases of reinfection then be examples of people
who happened to have weaker immune systems?
Or are
these cases any indication that our immune systems may not be able to
consistently build up enough protection against SARS-CoV2? Well, a review article published in January 2020 in the Journal
of Medical Virology summarizes much of what
is known about your immune system’s response to various types of coronavirus.
As you can see, this involves a complex orchestra of different cells and
chemicals. Therefore, the immune response to one virus won’t necessarily be the
same as to another virus, even if both viruses were different types of
coronaviruses. All of this also depends on how strong your immune system may be
and how well your immune system recognizes an invader like SARS-CoV2.
Plus,
your immune system has got to remember the virus. Over time, immunity may fade,
allowing the virus to reinfect you. It’s like when you get back together with
an ex after you have forgotten how terrible you are for each other. The
question then is how long can your immune system remember SARS-CoV2?
With
SARS-CoV2 having emerged so quickly, there just haven’t been enough studies yet
on how your immune system may react specifically to SARS-CoV2 and how this may
differ from person to person. Therefore, we have to rely on studies of other
coronaviruses for now. The closest approximation is probably the even more evil
cousin of SARS-CoV2, the original SARS virus that caused the outbreak of
2002-2003.
In a study published in a 2007 issue of Emerging
Infectious Diseases, a
research team from the Shanxi Provincial Center for Disease Control and
Prevention in Taiyuan, China, followed 176 patients who had had severe acute
respiratory syndrome (SARS). On average, SARS-specific antibodies
remained at the same level in a patient’s blood for about two years. Then,
during the third year after infection, antibody levels tended to drop
precipitously. This suggests that immunity to the SARS virus may remain for two
to three years with reinfection possible after three years.
Keep in
mind though that antibody levels do not always correlate with immunity. They
can be like selfies on Instagram, only indirect measures of what’s really going
on at a deeper level. Some people may have immunity against a virus without
detectable antibody levels, and some people may be very susceptible to
infection even though antibodies are present. The only way to have determined
if the patients actually had immunity against the SARS virus would have been to
have re-exposed them to the virus and checked what happened. And that would
have been a horrible experiment to do.
The
other question is how many different versions of SARS-CoV2 may be running
around, or rather spreading around since viruses don’t have little feet and
little sneakers. It’s difficult to answer this question for sure without more
thorough and widespread testing. According to a study published in the journal National
Science Review, an analysis of samples from 103 COVID-19
cases suggests that at least two different versions of SARS-CoV2 are
circulating. This doesn’t necessarily mean that these versions are so different
that immunity to one version doesn’t mean immunity to another. Regardless,
things may evolve in the near future. Viruses can be like the characters
in Game of Thrones or an actor in a Broadway show, changing
rapidly. Over time, the new coronavirus could possibly mutate to the point that
new versions are no longer as recognizable by your immune system as the
original version. After all, mutations are probably what allowed the virus to
jump from another animal to humans.
Not
knowing exactly how immunity against SARS-CoV2 works and how long it may last
throws a gigantic wrench into public health planning. Many trying to predict
the course of the pandemic have been assuming that once a high enough
proportion of the overall population has been infected and has become immune,
the pandemic will subside. Herd immunity is the percentage of the overall
population that is immune to a given pathogen. When this percentage gets high
enough, the virus will struggle to find more susceptible people to infect, sort
of like trying to sell Justin Bieber T-shirts in a crowd when most of the people
are already wearing such shirts. The belief is that when around 70% of the
population is immune to the virus, SARS-CoV2 will struggle to continue
transmitting.
However,
things could change substantially if people can actually get re-infected with
the virus or different enough versions of the virus end up circulating. Such
possibilities would be yet more reasons to question the “herd immunity”
approach to controlling the pandemic that’s currently being discussed in the
U.K. and described by Sarah Boseley for The Guardian. Since
there is no vaccine available against SARS-CoV2, there is actually talk of
allowing those with stronger immune systems to get infected to achieve the 70%
or so herd immunity threshold. Huh?
This
strategy would make sense except for the fact that it doesn’t.
First of all, those who get infected could end up having serious consequences
such as death, which is typically a very serious consequence. This would be
reminiscent of the saying that “the operation was successful, but the patient
died.” Allowing people to become infected by a potentially deadly virus is
always a risky proposition, sort of like playing roulette when your lungs are
on the betting table. So far, the COVID-19 case-fatality rate seems to be
somewhere between 1% and 3.4%. This isn’t as high as the rate for SARS but
nonetheless significantly higher than that of a bad flu season.
Secondly,
this herd immunity strategy depends on people not getting re-infected with the
virus. But with the aforementioned reports from Japan and China, you have to
wonder if the strategy is not a “herd immunity” strategy but rather a “herd
immunity maybe” strategy to borrow the words of Carly Rae Jepsen. “Maybe” may
work to some degree with flirting and dating but not when lives are at stake.
Third
of all, this strategy assumes that people will not leave or enter the U.K. That
may work only if you want to completely eliminate travel to and from the
country.
Finally,
such a strategy would run counter to other mitigation strategies such as social
distancing as indicated by the following tweet:
Uh,
U.K., would this really be O.K.?
All of
this is a reminder that scientists do not yet know enough about this new
coronavirus. What percentage of people become immune to the virus if exposed?
How strong is the immunity? Will it actually prevent reinfection? How long
would this immunity last? Is it two years as the SARS study hints at or could
it be much shorter than that? How does all of this vary from person to person?
How many different versions of the virus may end up circulating? As the
Internet meme goes, I and many other scientists have so many questions.
Therefore,
if you do get exposed to the virus and recover, don’t view it as a free pass to
start hugging strangers, digging your fingers deep into your nose like you are
looking for pocket change, and licking door knobs. Keep doing what everyone
else should be doing such as social distancing, washing your hands
frequently and thoroughly, keeping your filthy fingers from gravitating towards your
gigantic face, and actively disinfecting surfaces, objects, and that enormous
BTS statue that you have in your living room. Just because you survived the
first infection, doesn’t necessarily mean that future exposures and possible
infections will end up OK. As you know, sequels don’t always have the same
endings.
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