How is immunosuppression against COVID investigated?
There are several ways to do this. One way is to see if people who have been vaccinated are getting the coronavirus. And the other is to look at the levels of various components of the immune system in vaccinated individuals and how they change over time.
Is immunity weakening?
The answer from numerous studies seems to be in the affirmative, although it is worth remembering first and foremost that no vaccine is 100% protective, and as more people get vaccinated, those who get sick are more likely to get vaccinated.
But what is behind the apparent decline and what it means in practice and for booster (repeated) injections is less clear, The Guardian notes.
Data from Israel, where 78% of people aged 12 and older are fully vaccinated, have shown significant increases in infection rates in recent months.
Meanwhile, data from the British app Zoe Covid Study, where users can record whether they’ve been vaccinated, test results and COVID symptoms, showed that protection against infection after two Pfizer / BioNTech injections dropped from 88% in one month to 74% after five – six months, while protection against infection after two Oxford / AstraZeneca shots dropped from 77% to 67% after four to five months.
Professor Tim Spector, the lead scientist involved in the study, says: “In my opinion, under a reasonable worst-case scenario, the protection of the elderly and healthcare workers could be below 50% by winter.”
But, as experts note, such results are likely due to many factors, and not simply to the fact that the protection provided by vaccination ceases to work.
COVID-19 vaccines are somewhat less effective against the Delta option than against the Alpha option. The Delta coronavirus is also more contagious, which – along with policy changes such as easing restrictions – means that the chances of someone being exposed to the virus have increased.
And there is the complication that among those who were first vaccinated were the most vulnerable people with weak immune systems, who may be more susceptible to “breakthrough” infections.
Another factor is that the Zoe Covid Study is based on a sample of app users who choose their own. “We have to be careful with mistakes,” warns Deborah Dunn-Walters, professor of immunology at the University of Surrey, adding that the Zoe research team has also noted such problems.
Professor Dunn-Walters argues that it is also possible that many vaccinated people may be asymptomatic, meaning that their infection may go undetected.
But most of all, hospitalizations and deaths are of concern. “This latest Zoe study confirms that there is a decline, but it is not yet clear what this means for disease severity, a key aspect of vaccine protection,” said Professor Ian Jones, professor of virology at the University of Reading, England.
Other studies have shown that the biological components of immunity can weaken over time, including the work of University College London’s Virus Watch, which showed that in some cases the number of antibodies produced in response to two doses of Oxford / AstraZeneca and Pfizer / BioNTech vaccines dropped more than than 50% in 10 weeks.
However, the World Health Organization (WHO) has said it is unclear if studies showing that a decrease in antibody count is a decrease in the effectiveness of the vaccine.
Moreover, antibodies are only one component of the immune system and, according to experts, a decrease should be expected. Memory B cells and T cells that last longer are also critical, but more difficult to measure.
“These are memory B cells and T cells that can be recruited very quickly in any response to fight future infections,” says Professor Dunn-Walters, adding that at least one study has looked at post-vaccination immunity Injection with Pfizer / BioNTech found that memory B cells were still present after six months.
Scientists are still working to understand what levels of these various components of the immune system are required to protect against infections and serious illness.
Does this mean that booster vaccinations are needed?
As noted by The Guardian, at this point it seems likely that the UK plan for the Joint Committee on Vaccinations and Immunizations (JCVI) is to offer repeated shots only to particularly vulnerable people, such as people with weakened immune systems, which means that in Britain most people will not receive their third vaccination this fall.
Professor Adam Finn, a member of the Joint Committee on Vaccines and Immunizations, told BBC Radio 4 that studies have shown that COVID vaccines continue to provide good protection against serious illness and hospitalization.
“But we need to be very careful to see if this weakening leads to milder illnesses leading to more severe cases, because then repeated shots will be required,” he said.
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