Hello, and welcome to my channel Medicine with Dr. Moran. I'm Dr. Keith Moran.
Today I want to talk about new natural immunity research published in the peer-reviewed journal of
the American Medical Association It was published just this past week now there's a link to the
research in the description below. The researchers were from Johns Hopkins and what they wanted to do
was to look at the durability of immune response in people who had recovered from previous Covid-19
infection. They recruited participants who had never been vaccinated via a single public twitter
post and a single public facebook advertisement in the fall of 2021. The participants who
responded to these two posts completed an online questionnaire about demographics,
mask use, and Covid-19 status. The investigators then created three equally sized sample groups
among these unvaccinated participants. Group one were those who reported previous documented Covid
infections such as with a positive PCR. Group two were those who believed they had Covid but were
never tested and group three were those who did not believe that they ever had Covid. They tried
to match all three groups by age race, ethnicity, and education. There were 1,580 individuals who
responded to the posts and completed the online questionnaire. The participants were asked to
have their blood work drawn just once over the next six weeks. Now only 52% of them actually did
so which was a total of 816 people who agreed to participate in the study. The average age was 48
and 52% were women with 82% being white. Two blood tests were ordered one was for antibodies to the
receptor binding domain RBD for short or otherwise known as antibodies to the spike protein.
The other tests that was done were antibodies to the nucleocapsid portion of the virus.
What would these two tests tell us? First of all if you have antibodies to the nucleocapsid
portion of the virus it means that you've actually seen the virus before in other words you've been
naturally infected. The only other time you might have antibodies to that part of the virus would be
if you've received a vaccine that used the whole virus and what they do is they take the virus and
they inactivate it and an example of this is the Coviaxin vaccine. Now Covaxin is not being
used in the U.S. so in this study antibodies to the nuclear capsid antigen indicates previous
infection. If you have antibodies to the RBD portion of the spike protein then that would
indicate that someone's either been previously infected or been vaccinated with a vaccine that
generates antibodies to the spike protein which all of the vaccines in the U.S. currently do.
I have ordered these two tests on several patients in my practice and in fact I had these tests
done recently on myself. I personally had two significant exposures recently as my daughter,
son and wife all developed mild Covid symptoms during the Omicron wave. None
of them were really sick. Two of our cats actually developed respiratory symptoms
Sweetie and Rolls developed those. Rolls is named for his jelly roll pattern on his fur.
Two other cats were unusually lethargic for a few days. Mitz which is known for his polydactyl paws
and Jag who is a black cat obviously that's why we called him Jag. Our cat Puffy also was
really cranky for about four days as well. We do have one well done study looking at Omicron
transmission rates secondary attack rates in households and it's about 30% if you're wondering.
In addition one of my staff members that I work closely with was unwell with Omicron for a few
days as well. I personally woke up with a dry throat a couple of days in a row which
went away quickly with a hot cup of tea in the morning but I had no other symptoms and so I did
wonder given the amount of exposure that I had whether I actually in fact got the infection.
Here are my results. As it turned out I did not have antibodies
to the nuclear capsid antigen which is the first test on the slide and that indicates that I had
not got an infection with Omicron like my three family members and probably five of our cats.
Now the second test on the slide indicates that I still had good levels of antibodies
against the spike protein indicating my vaccination status as I am vaccinated.
In summary these are the tests that are being used in this research study. Now on this slide
is a list of the demographics of the participants in each of the three groups. Remember all three
groups were unvaccinated and the first group who had test confirmed Covid-19 infections the second
group were people who believe they previously contracted Covid but were not tested and the
third group are people who believe that they never got Covid at any point. Now on to the results. In
the first group the people with no vaccination who previously had Covid confirmed by previous testing
you can see that 280 of them or 95% were positive for the Nucleocapsid antibody and 293 or 99%
were positive for antibodies against the Receptor Binding Domain of the spike protein. In this
group the average number of days since Covid-19 diagnosis was 261 or 8.7 months
but the range here is quite wide and actually goes out to almost 650 days which is 1.8 years.
There actually was no evidence of an association between time after infection and antibody titer as
you can see on this graph. Looking closely on the graph you can see that some people were diagnosed
recently within the first 50 days but there were a few people that were beyond 500 days. The orange
line on the graph going across is the line of best fit for the data and it's completely flat
as there's no association as I mentioned between antibody level and day since Covid diagnosis.
Each dot of course is a single person and there's only a single dot on the graph for each person.
In a previous video that I made many months ago a group of researchers looked at antibody levels
with time in a number of participants who had not been vaccinated but had recovered from Covid in
other words natural immunity. The researchers in this study found a very slow reduction in antibody
levels which I'm going to show on this graph and if you look with time what they did was they
ultimately extrapolated the data and they found that the average person might have antibody levels
out to five years. Obviously a lot would depend upon the individual's health and you do have to
remember that antibody levels are being used as a surrogate to try to predict the likelihood of
subsequent infection. Higher levels do predict a lower likelihood of symptomatic infection. What
we really want to know though is how functional are those antibodies against the current variant.
In other words how well do these antibodies neutralize the latest variant du jour.
You can obviously have antibodies but if they don't neutralize the variant well
then you're more likely to have a symptomatic infection. You can obviously have antibodies
but if they don't neutralize the variant well then you're more likely to have a symptomatic
illness on exposure to the virus. We know that with Omicron you need to have significant antibody
levels in order to neutralize Omicron compared to previous variants such as Alpha and Delta.
One of the other things that we've seen with Omicron is that people who have been vaccinated
as well as people with natural immunity both have developed symptomatic infections
because the antibodies that they have made against the original strain in the case of
the vaccinated people and of course in the case of natural immunity the antibodies that
you would make with that would be against whatever strain you get infected with.
So if you're infected with Omicron you're going to make antibodies preferentially towards that
but some of those obviously would help you if you were to get Alpha or Delta. Given that Omicron
has a number of receptor binding domain mutations over in 30 in fact that it's able to evade some of
the antibodies that people have and that's why boosting people with vaccination will increase
the number of antibodies overall and give people a better chance to neutralize the virus. Now getting
back to the Johns Hopkins study if you look at the group who were not vaccinated who thought they
had Covid actually 55% of them tested positive for receptor binding domain spike antibodies.
So only about half of the people in that group who thought they had Covid actually did.
Among the third group which were those who had not been vaccinated and did not
think that they ever had Covid 11% tested positive for the anti-RBD antibodies. This goes to show
that there are a lot of people in the world who did get exposed to the virus and did get infected
but had either no symptoms or minimal symptoms to think that they'd never had the infection
and this of course is in the adult population in this study. Children of course are much more
likely to be asymptomatic than adults and we know from antibody studies and children that around 40%
of American children before vaccination actually had Covid. This I think is one of the many reasons
why Sweden has chosen not to vaccinate healthy kids between 5 and 12. Many countries have done
things differently through this pandemic and the one thing to always remember is that if different
countries are doing different things then it means that there's clearly a difference of opinion in
the best course of action. In other words the best course of action is not definitively known.
While there are many examples in this pandemic I can certainly point to masking in children
where there's been quite a bit of discrepancy. The WHO position was not to mask children under six
and in the UK I understand that they did not mask under the age of 12. Whereas in North America
everyone above the age of two were masked. The authors of the John Hopkins study concluded by
saying that anti-RBD levels were observed after positive Covid-19 test results extending up to
20 months which extends previous durability data. Obviously antibody levels alone do
not directly equate to immunity but the fact that the levels were durable is certainly encouraging.
Obviously these antibody levels may not correlate with protection against future variants of the
virus but that's no different than people who have been vaccinated. As I've mentioned in other
videos the long-term cellular memory compartments of the B cells as well as T cells have been shown
to about a year in people with natural immunity as well as a shorter period of time in those who
are vaccinated. These T cells in particular are what's going to prevent us from severe infection.
The original Sars coronavirus did lead to long-term T-cell memory
which has been shown up to 18 years after previous natural infection with that coronavirus.
There's another interesting study I want to tack on to this video. This is on antibodies again
this has to do with natural immunity as well and this studies from the Journal Vaccines. It's from
mid-January and it compared two doses of Pfizer vaccine in Israel to recovered people without
vaccination. There were 2,653 individuals with two doses of Pfizer during the study period and
4,361 recovered patients who had natural immunity and what they found was that the initial antibody
levels in vaccinated people were initially much higher than the recovered individuals.
This is the graph of the antibody decline but the levels in the vaccinated group drop by a
significant amount 38% per month while people with natural immunity they decrease by less
than 5% per month. Here is the graph of the recovered or natural immunity participants.
Six months after two doses of Pfizer 16% of subjects had antibody levels below the
threshold of the test while only 10% of recovered people were below that after nine months so three
months later from their infection. So the study demonstrates that individuals who receive Pfizer
vaccination have different kinetics of antibody levels compared to people who had been infected
with SARS Cov2 with initial higher levels but a much faster exponential decrease in the Pfizer
vaccine group. To conclude I want to say that just because I'm talking about natural immunity today
does not obviously mean that I recommend that people get their immunity through this infection.
Vaccination especially for those that are high risk due to age and comorbidities is certainly
the safest way to develop a degree of immunity from this virus. I'd like to thank you for
watching today on Medicine with Dr. Moran. I'm Dr. Keith Moran. Get healthy and stay healthy.