Severe dose of Covid offers better protection against new variants

Study also finds vaccinated people have greater resistance to new strains of the disease

A member of medical staff takes coronavirus test samples of a woman during drive-through coronavirus testing at a converted ice rink, in Alkmaar, the Netherlands. Reuters

Fully vaccinated people or those who have previously suffered severe Covid-19 may be at lower risk of catching a severe dose of a new variant than those who have had milder cases, a study suggests.

Scientists analysed serum samples from 69 Covid-19 patients and 50 fully-vaccinated health workers.

The study by Amsterdam University Medical Centre found that while all subjects showed a reduced response to the alpha, beta, and gamma variants, compared with the original strain, vaccinated people and those with severe enough Covid-19 to require hospital treatment had adequate antibody responses.

In contrast, patients who had experienced mild Covid-19 infections had lower antibody responses to the original virus and often showed no response to the beta and gamma variants.

Doctors have reported a rise in patients testing positive for Covid a second time.

People infected with the Covid-19 delta variant are also twice as likely to be taken to hospital than those infected with the alpha variant, a recent study found. The risk of being admitted to hospital at an early stage was also higher, researchers found in the largest study to date, in which 40,000 cases in England were analysed.

In the latest study, some relief was given for people who may fall ill with a new variant.

“An implication of this study could be that infections with new [variants of concern] will become more prevalent, especially later on when antibodies have declined,” Tom Caniels and colleagues wrote in the journal Science Advances.

“However, the question remains whether infection with an emerging, antigenically altered variant will result in a less severe course of infection.”

Mr Caniels explained his research to The National:

He said: “In response to infection, certain immune cells called B cells make antibodies, that latch on to incoming viruses and 'flag' them — as such, these viruses cannot infect other cells and other components of the immune system are stimulated to destroy these viruses.

“In people that have severe Covid-19, the infection generally takes a longer amount of time than in those that have only mild symptoms. Moreover, the immune system in people with severe Covid-19 becomes over-activated — both of these factors contribute to more antibody production in people with severe Covid-19 compared to mild Covid-19. You can imagine that people with higher levels of antibodies also have a more diverse pool of antibodies and can thus more easily recognise viral variants.

“This is exactly what we see happening here: people with high antibody levels after infection [i.e. those with severe Covid-19] generally recognise viral variants better. The kicker is that vaccines do a very good job at inducing similar high levels of antibodies as we see in severe Covid-19. That’s great news, because that means vaccine-induced antibodies are also generally very apt at recognising viral variants such as the ones studied here, but also probably variants that are yet to emerge.”

He said the study confirmed that vaccines also work extremely well against viral variants; that people that experience only mild Covid-19 benefit from getting a vaccine, and getting a vaccine hugely boosts the antibody levels and also diversifies them, increasing the likelihood they can help protect against future infection with a variant.

Globally spreading variants, including alpha (B.1.1.7, first detected in the UK), beta (B. 1.351, first detected in South Africa), and gamma (B. 1.1.28. P1, first detected in Brazil) have raised concerns about whether vaccine or original strain-induced immunity can protect against variant Covid-19 infections.

To investigate the threat posed by these variants, the team assessed patients in the Netherlands, who were sampled four to six weeks after symptom onset between March 2020 and January 2021, and health workers who had received two doses of the Pfizer-BioNTech vaccine.

They found a particularly large discrepancy between hospital and non-hospital Covid-19 patients’ potential to fight the beta variant — while serum from hospital patients neutralised this variant about as well as vaccinated people, 39 per cent of non-hospital sufferers showed no detectable neutralisation against beta.