Hello and welcome to my channel Medicine with Dr. Moran. The Journal the Lancet
recently published a systematic review and meta-analysis on natural immunity now three
years into the pandemic. They took a look at 65 studies from 13 different countries.
This of course has been a taboo subject but finally it's been getting more light shed on
it over the past year. I've published an extensive playlist of studies over the last two years on the
subject as data has been published. It's something that I've been frequently asked about by patients,
friends, and family. Now natural immunity this refers to the condition where someone through no
fault of their own acquires an infection survives and makes antibodies as well as memory cells
against the infection which provide protection against re-infection from the same virus.
Obviously, there's survivorship bias as not everybody survives the initial infection.
Now with respect to SARS Cov2 with the virus that causes Covid-19 there is highly variable
risk when it comes to severe disease that leads to hospitalization or even death. I've reported
extensively about risk in regard to the different age groups as well as comorbidities on my channel.
Now perception of risk has been poorly articulated in the media which led me initially to be making
videos as fatality rates were quoted in the 2 to 10% range which were grossly misleading when the
real infection fatality rate for everyone with no immunity was much lower on the order of 0.25% as
reported by the U.S. CDC. This figure of course is markedly higher for people over the age of 80
with comorbidities and no immunity which can be 5% or even more but it's markedly lower in
healthy people under the age of 30. A German study showed no deaths in children from 5 to 11. So,
there's quite a significant gradation of risk even in non-immune people and by non-immune I mean
people that have not been vaccinated or infected. Many people not to mention political figures
either overestimated or underestimated the risk of severe disease. That's where Physicians could have
been quite helpful advising people of their actual risk and trying to get people to be healthy.
So why is natural immunity important? Well this is something that our bodies deal with on a regular
basis. We get respiratory infections from many different viruses on a regular basis. We develop
antibodies to these viruses which ultimately wane with time but we also develop cellular immunity
from our memory B and T cells which in the case of many viruses allow us to fend off viral infections
even years later preventing us from ending up in the hospital or even dying. As the antibodies wane
protection against re-infection with symptoms only lasts a short duration typically months and we can
get reinfected by the same virus all over again but the protection against severe disease can last
much longer. This is simply how our immune system works. It's what we learn in medical school.
Every physician knows this every student learning Immunology learns this this is why it's
difficult to understand why this whole concept of natural immunity was ignored by many countries.
As this virus of course spread out through the world many people through no fault of their own
happen to get infected. It might have been you. This is simply a fact of life when we have very
transmissible respiratory viruses. You can't shame people for picking up infections which
unfortunately is what happened in many cases and Physicians cannot ignore their patients or not
treat them just because they got infected. It's our duty to care. We knew early on people who got
infected did not seem to be getting reinfected in other words they had some degree of protection.
Now with each virus understanding natural immunity is important so that we understand what kind of
protection previous infection gives to people. If the protection is significant then these people
might not need to be vaccinated if a vaccine becomes available or at least they could have
lower priority for vaccination while other people who are non-immune get vaccinated first. That was
something that was lost in this particular pandemic. It was not even considered by many
countries. Vaccine passports that allowed people to move freely were only given in some countries
to people with antibodies against the vaccine but completely ignored the antibodies that were
generated by natural infection. It seemed bizarre to me that governments would accept the antibodies
made by the vaccines which were only to the spike protein of course but were ignoring antibodies
made to the real virus through natural infection which of course were broader because people who
were naturally infected did not just develop antibodies against the spike protein but they
also developed antibodies against the rest of the virus. So, what did the Lancet systematic
review tell us? Well here's the study and of course as always there's a link to the study in
the description below if you're interested. The background statement in their summary I thought
was interesting because this was ignored by many countries and they state "Understanding the level
and characteristics of protection from past SARS Cov2 infection against subsequent re-infection
symptomatic Covid-19 disease and severe disease is essential for predicting burden
for designing policies that restrict travel or access to venues where there's high risk
of transmission and for informing choices about when to receive vaccine doses." To summarize
the results they looked at these 65 studies from 19 different countries and they reviewed
protection against the Original ancestral strain as well as Alpha, Beta, Delta, and the initial
Omicron variant. As I reported on the channel protection from reinfection declines over time and
at 40 weeks they found protection from reinfection from the original Alpha and Delta variants was 78%
but protection against reinfection by Omicron decline much more rapidly and was 36% at 40 weeks.
The more important data is what is the protection against severe disease? This remained high for
all variants at 90% for the original Alpha and Delta variants and 89% for Omicron at 40 weeks.
Their summary statement was that "Immunity conferred by past infection should be weighed
alongside the same protection that you might get from vaccination when assessing future disease
burden. It provides guidance on when individuals should be vaccinated and designing policies that
mandate vaccination workers or restrict access on the basis of immune status to settings where the
risk of transmission is high such as travel or indoor settings." They also state that "Although
protection from reinfection from all variants wanes over time our analysis of the available data
suggests that the level of protection afforded by previous infection is at least as high, at least
as high, if not higher than that provided by two doses of the vaccine using a high quality MRNA
vaccine Moderna and Pfizer." I and others have been making all of these points for a long time
and of course this is just simply basic Immunology 101,
but obviously with any new virus one must do the research to understand the specifics of natural
immunity as well as immunity from vaccination. The general public do need to understand the
word immunity is not the absolute or what we call sterilizing immunity where someone gets infected
or is vaccinated that they will never ever get the disease. In addition people who are currently
well protected against this virus will have their immunity waning over the years or decades and it's
highly likely that they may not get severe disease now but when they get into their older years or
if they become immunocompromised this virus could cause severe disease or even death down
the road. The vast majority of the world has been infected by this virus at this point and of course
many people have been vaccinated as well. It's interesting to me to note that the United States
still does not allow visitors who are unvaccinated this policy of course has led to some high-profile
people not being able to visit such as the world number one tennis player Novak Djokovic who has
been infected at least once that I'm aware of. So this systematic review tells you that his natural
immunity is at least as good if not better as two vaccinations but people who have had two
vaccinations can enter the United States where is he cannot. Many spectators in fact in the stands
in the tennis world have never been vaccinated and of course they're allowed to attend the
tournament. I'm not sure whether other countries are still doing the same as the United States
please comment below if this is still the case in your country I would be interested to know.
Thanks a lot for watching my presentation today. Remember get healthy and stay healthy.