Home Business Covid vaccines: How immune imprinting can help experts rethink shots?

Covid vaccines: How immune imprinting can help experts rethink shots?


A spike in Covid-19 hospital admissions caused by the Omicron BA.5 subvariant, coupled with the failure of vaccines to prevent reinfection, has prompted health leaders to rethink their approach to accelerators.

US regulators last week recommended that the vaccines be redesigned to produce a new booster targeting Omicron — the first change in the composition of vaccinations since their introduction at the end of 2020. Research on immune imprinting, in which exposure to a virus through infection or vaccination determines a person’s level of protection, is now sparking a makeup debate. vaccines against Covid-19.

Immunologists say that after more than two years the coronavirus pandemicpeople acquired very different types of immunity to the Sars-Cov-2 virus depending on which strain or combination of strains they were exposed to, leading to large differences in Covid-19 outcomes between individuals and countries.

“The effect is more subtle than ‘the more times you have it, the less protection you get,'” said Professor Danny Altman of Imperial College London, who is researching the phenomenon with colleagues. “It’s more useful to think of it as a progressive refinement of a huge repertoire. Sometimes it will be beneficial for the next wave, sometimes not.’

What is immune imprinting?

After someone first encounters the virus through an infection or vaccination, the immune system remembers its initial response in a way that usually weakens the response to future variants of the same pathogen, but can sometimes amplify it. Proteins on the “spike,” which the virus uses to bind to human cells, play a key role.

“Our first encounter with a spike antigen, either through infection or vaccination, shapes our subsequent pattern of immunity through immune imprinting,” said Professor Rosemary Boyton of Imperial College.

The pattern has been observed for many years in influenza and dengue viruses, when they were commonly referred to as original antigenic sin. Research now shows that this is also true of Sars-Cov-2, although the implications are hard to pin down, according to Altman, who prefers the term “immune imprinting” to the biblical connotations of original sin.

A diagram explaining the concept of immune imprinting and how it works

A study of 700 UK healthcare professionals by the Imperial team, published last month in the journal Sciencefound that Omicron infection had little to no beneficial effect on boosting any part of the immune system—antibodies, B cells, or T cells—among people who had been infected with earlier variants of Sars-Cov-2.

“Far from being a benign natural booster of vaccine immunity as we might have thought, Omicron is a particularly stealthy immune booster,” Altman said.

The vaccines currently in use were developed to fight the virus when it first emerged from Wuhan, China, more than two years ago. They retain high protection against serious illness and hospitalizations, but their effectiveness against transmission of infection and mild infection is rapidly weakening, especially against Omicron.

Understanding the effect of immune imprinting will help health officials decide which vaccines to use in future immune boosting campaigns. Boyton said immune imprinting has “important implications for future vaccine development and dosing strategies.”

Does immune imprinting help explain breakthrough infections?

Most people in industrialized countries have been infected or vaccinated against Covid — or both. A school infection survey in England, run by the London School of Hygiene and Tropical Medicine, published data last week showing that 99 per cent of secondary school children tested positive for Covid antibodies from natural infection.

At this stage of the pandemic, the vast majority of Covid cases are re-infections in people whose immune defenses, derived from vaccines or previous infections, cannot withstand Omicron BA.4 and BA.5.

And these “breakthrough” infections aren’t necessarily as mild as many people think, said Ziad Al-Ali, a clinical epidemiologist at Washington University in St. Louis. He analyzed the medical records of 34,000 people with breakthrough Covid infections in the database of the US Veterans Administration, which provides medical services for retired soldiers. The cumulative risk of serious damage to the heart, brain, and lungs increased significantly with each re-infection.

In another study, Al-Ali and colleagues found that while vaccines are good at preventing acute Covid-19 disease, they were only 15 percent effective at preventing prolonged Covid disease, defined as suffering symptoms for 12 weeks or more after Covid -19. 19 diagnoses. “Covid infection, even among vaccinated people, seems almost inevitable these days,” he said.

Has immune imprinting influenced the vaccine debate?

Some anti-vaxxers cite immune imprinting in their arguments on the grounds that vaccines become less effective as the virus evolves, an objection that immunologists vehemently reject.

“While our latest findings highlight obvious concerns about the nature of Omicron infection, vaccination remains effective against severe disease,” Altman said. “Those who are eligible for a booster should be encouraged to do so.”

Professor Christian Drosten, a leading German virologist, told Der Spiegel that increasing the interval between injections could help reduce the impact of immune imprinting.

“I suspect that the effect [of vaccination] will improve the longer the interval from the previous vaccination,” he said. “[But] How long the interval between vaccinations should be is still unknown.

How has differential immunity affected vaccine decisions?

Last month, the World Health Organization said Omicron-based shots could be useful as boosters because they would extend protection against multiple variants.

And on Tuesday, a U.S. Food and Drug Administration advisory committee voted 19 to two to include genetic material from Omicron in the new booster shots.

“We’re trying to use everything we can from predictive modeling and data to try to get ahead of the virus, which has been very tricky,” said Peter Marks, director of the FDA Center. for evaluation of biologics and research.

On Thursday, the FDA recommended the inclusion of the Omicron BA.4/BA.5 subvariant component in a new injection for fall health promotion campaigns. But the agency did not recommend changing the existing vaccine for the first doses.

Moderna and BioNTech/Pfizer, leading manufacturers of mRNA vaccines, presented laboratory data showing that their latest versions targeting Omicron generate strong antibody responses against BA.4 and BA.5. But some immunologists remain uncertain whether they will be more effective than receiving another dose of the original Wuhan vaccine.

“Due to immune imprinting, patterns of anti-adhesion immunity have become heterogeneous, complex and unpredictable in different individuals and populations,” Boyton said. “It makes the case for moving forward cautiously, thoughtfully and based on facts.”

“The challenge for the next generation of Covid vaccines is to develop vaccines that augment the immune response to protect against future variants of concern.”

This article is first published on Source link

Previous articleUber releases safety data: 998 sexual assault incidents including 141 rape reports in 2020 | Crime
Next articleMartina McBride. Good genes or good papers?!