Why the Delta Variant Makes Vaccination More Necessary, Even If You Had COVID-19

A person can develop immunity, the ability to resist infection, in two ways: after being infected with a virus or after a vaccination. However, immune protection is not always the same. Led by Jennifer T. Grier, immunologist at the University of South Carolina, a recent document was published where The vaccines and the antibodies they generate against the Delta variant are analyzed.

Based on more than a dozen recently published scientific papers, the specialist said that immunity to the vaccine and natural immunity for SARS-CoV-2 may differ in terms of the strength of the immune response or duration of immunity. protection. In addition, “not everyone will achieve the same level of immunity against infection, while immune responses to vaccines are very consistent.”

The difference in immune response between vaccination and infection appears to be even greater when it comes to newer variants. In early July, two new studies were published showing that COVID-19 vaccines, although slightly more effective against older strains of the virus, always seem to provide an excellent immune response against the new variants. Researchers looked at how antibodies bind to newer variants of the coronavirus and found that people previously infected may be susceptible to the new strains, while those vaccinated were more likely to be protected.

“COVID-19 vaccines offer a safe and reliable route to immunity against older strains of coronavirus and emerging strains, especially the new delta variant,” Grier said.

Immunity comes from the immune system’s ability to remember an infection. With this immune memory, the body will know how to fight the disease if it encounters the pathogen again. Antibodies are proteins that can bind to a virus and prevent infection. T cells direct the elimination of infected viruses already bound by antibodies. These two are some of the major players that contribute to immunity.

After infection with SARS-CoV-2, a person’s antibody and T cell responses may provide protection against reinfection. About 84% to 91% of people who have developed antibodies to parental coronavirus strains are unlikely to be re-infected. for six months, even after a mild infection. People who have not shown symptoms during infection are also likely to develop immunity, although they tend to produce less antibodies than those who felt sick. So, for some people, natural immunity can be strong and long lasting.

A big problem is that not everyone will develop immunity after infection with SARS-CoV-2. Up to 9% of those infected do not have detectable antibodies and up to 7% do not have T cells that recognize the virus 30 days after infection.

“For people who develop immunity, the strength and duration of protection can vary widely,” Grier explains. Up to 5% of people can lose their immune protection within months. Without a strong immune defense, these people are susceptible to reinfection by the coronavirus ”. Some have had second episodes of COVID-19a months after your first infection; and, although this rarely happens, some people have been hospitalized or even have muerto dnear reinfection.

A growing problem is that people who have been previously infected with strains present earlier in the pandemic may be more likely to be re-infected with the delta variant. A recent study found more than 12 months after infection, 88% of people still had antibodies that could block infection of cultured cells with the original variant of the coronavirus, but less than 50% they had antibodies that could block the delta variant.

In addition, an infected person can also transmit the coronavirus, even without feeling sick. The new variants are particularly problematic in this case, since they are transmitted more easily than the original strains.

COVID-19 vaccines generate responses so many T-cell type antibodies , and these responses are much stronger and more consistent than immunity after natural infection. One study found that six months after receiving their first dose of Moderna vaccine, 100% of people tested had antibodies to SARS-CoV-2. This is the longest period that has been reported in studies published to date. In an article that looked at the Pfizer and Moderna vaccines, antibody levels were also much higher in people who had been vaccinated than in those who had been vaccinated. recovered from infection.

Better yet, a study in Israel showed that the Pfizer vaccine blocked 90% of infections after the two doses, even with new variants present in the population. And fewer infections mean people are less likely to transmit the virus.

“For those who have already been infected with the coronavirus, there is still a great benefit to getting vaccinated,” Grier said. A study with the original COVID-19 virus showed that vaccination after infection produced about 100 times more antibodies than infection alone, and 100% of people vaccinated after infection had protective antibodies against the infection. delta variant.

“COVID-19 vaccines are not perfect,” the specialist concluded, “but they produce strong antibody and T cell responses which provide a safer and more reliable means of protection than natural immunity, especially with the swarming of new variants.

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