What immune imprinting means for the future of COVID-19 vaccines
When AstraZenecaTrusted Source, Pfizer, and Moderna started to recruit participants
for their first COVID-19 vaccine trials in the spring and summer of 2020, they
had to find people who did not think they had previously been infected
with SARS-CoV-2, the virus that causes COVID-19.
Pharmaceutical companies took this measure for a number of
reasons — for example, the world had little idea how much previous infection
with SARS-CoV-2 might protect against future infections.
Without this information, it was difficult to evaluate how much
of the protection discovered in the trial was due to the vaccine or to previous
exposure to the virus. This presented some challenges.
In fact, in areas heavily impacted by the virus in the first
wave, the requirement to recruit participants with no previous infection was
met with some initial reactions of disbelief.
Community testing had not been in place for months in many
places, some people would have had asymptomatic infections, and it is also
likely people had COVID-19 before they understood it was circulating
in their region.
And of course, no trial participants had, in the beginning,
received any other form of COVID-19 vaccine as they did not yet exist.
Research has since shown that previous SARS-CoV-2 infection alongside
vaccination offers the strongest protection against future
infection, that mixing and matchingTrusted Source vaccines
works, and that immunity from COVID-19 wanes with time.
Our understanding of the virus has improved. We know how
it spreadsTrusted Source, how to protectTrusted Source against
it, and how to treatTrusted Source the
disease it causes. Yet, at the same time that this body of knowledge has grown,
our actual bodies have changed in how they might respond to a SARS-CoV-2
infection.
While in November 2019, very few people in the world had been
exposed to SARS-CoV-2, today, over 11 billion doses of
COVID-19 vaccines have been administered, and about 500 million people are
likely to have had COVID-19.
Of those individuals, some will have contracted the original
Alpha variant of the virus, some Delta, some Omicron, and some may have had
several infections with more than one variant.
Considering that, on top of that, many people will have been
vaccinated with different types of vaccines and different combinations of
vaccines, the ways in which our immune systems may have been exposed to
SARS-CoV-2 markers are myriad.
While many of us will be able to stage an immune response to
SARS-CoV-2 that we would not have been able to 2 years or even 1 year ago, the
individual response may vary considerably between people, depending on the
nature of previous exposure.
This phenomenon is known as immune imprinting, Prof. Danny Altmann, professor of immunology
at Imperial College London explained to Medical News Today in
an interview:
When AstraZenecaTrusted Source, Pfizer, and Moderna started to recruit participants
for their first COVID-19 vaccine trials in the spring and summer of 2020, they
had to find people who did not think they had previously been infected
with SARS-CoV-2, the virus that causes COVID-19.
Pharmaceutical companies took this measure for a number of
reasons — for example, the world had little idea how much previous infection
with SARS-CoV-2 might protect against future infections.
Without this information, it was difficult to evaluate how much
of the protection discovered in the trial was due to the vaccine or to previous
exposure to the virus. This presented some challenges.
In fact, in areas heavily impacted by the virus in the first
wave, the requirement to recruit participants with no previous infection was
met with some initial reactions of disbelief.
Community testing had not been in place for months in many
places, some people would have had asymptomatic infections, and it is also
likely people had COVID-19 before they understood it was circulating
in their region.
And of course, no trial participants had, in the beginning,
received any other form of COVID-19 vaccine as they did not yet exist.
Research has since shown that previous SARS-CoV-2 infection alongside
vaccination offers the strongest protection against future
infection, that mixing and matchingTrusted Source vaccines
works, and that immunity from COVID-19 wanes with time.
Our understanding of the virus has improved. We know how
it spreadsTrusted Source, how to protectTrusted Source against
it, and how to treatTrusted Source the
disease it causes. Yet, at the same time that this body of knowledge has grown,
our actual bodies have changed in how they might respond to a SARS-CoV-2
infection.
While in November 2019, very few people in the world had been
exposed to SARS-CoV-2, today, over 11 billion doses of
COVID-19 vaccines have been administered, and about 500 million people are
likely to have had COVID-19.
Of those individuals, some will have contracted the original
Alpha variant of the virus, some Delta, some Omicron, and some may have had
several infections with more than one variant.
Considering that, on top of that, many people will have been
vaccinated with different types of vaccines and different combinations of
vaccines, the ways in which our immune systems may have been exposed to
SARS-CoV-2 markers are myriad.
While many of us will be able to stage an immune response to
SARS-CoV-2 that we would not have been able to 2 years or even 1 year ago, the
individual response may vary considerably between people, depending on the
nature of previous exposure.
This phenomenon is known as immune imprinting, Prof. Danny Altmann, professor of immunology
at Imperial College London explained to Medical News Today in
an interview: