Only one dose of COVID-19 vaccine is enough after infection?

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Only one dose of COVID-19 vaccine is enough after infection?

Only one dose of COVID-19 vaccine is enough after infection? Although one can get strong protection after being infected by the new coronavirus, people still have concerns.

More and more studies have shown that many people infected with the new coronavirus may be able to safely skip the second injection of any two-dose vaccine regimen. These results may help expand scarce vaccine supplies and are already affecting vaccination policies in some countries. But it is not clear whether these findings apply to everyone and all vaccines, which affects how policymakers should respond.

Studies have shown that people who have been infected with SARS-CoV-2 in the past often have a strong immune response to a single injection, and the benefit of re-injection is not large. For people who gain immunity through infection, a single injection will usually increase the number of antibodies to the same level as an uninfected individual who has received two injections, or often higher than the latter.

France, Germany, Italy, and other countries now recommend that only one dose of the vaccine is given to people who have a healthy immune system and have been previously diagnosed. Many scientists who have studied the immune response to vaccination believe that this policy is a smart way to allow countries eager to vaccinate their populations to take full advantage of limited supplies.

Jordi Ochando, an immunologist at the Icahn School of Medicine at Mount Sinai in New York City, said that while millions of people are waiting for their first dose of vaccine, follow the current two doses of vaccine in previously infected individuals The vaccination plan is meaningless.

But scientists still don’t know whether a single-dose vaccine program for previously infected people will give some people sub-optimal protection. It is also unclear whether such plans are effective for all types of vaccines.

Giuliana Magri, an immunologist at the Hospital del Mar Research Institute in Barcelona, Spain, said that if you have been infected before, one dose may be enough. But how to put these experiences into practice? She admits that it is complicated.

Only one dose?

There is ample laboratory evidence that people who have previously been infected with SARS-CoV-2 can benefit from vaccination, which has prompted the World Health Organization (WHO) and other public health agencies to recommend that these people still be vaccinated. However, it is not clear whether they need to roll up their sleeves twice.

A paper published in the journal Nature on June 14 provides some up-to-date evidence that one dose is necessary for people who have been infected with COVID-19. A team of researchers at Rockefeller University in New York City and elsewhere studied 26 people who contracted the virus early in the pandemic. All of these people later received at least one dose of Pfizer-BioNTech or Moderna’s vaccine, both of which are based on messenger RNA (mRNA).

The researchers analyzed the levels of “neutralizing antibodies” in the participants’ bodies, which are effective immune molecules that prevent viruses from entering cells. At present, the number and vitality of a person’s neutralizing antibodies are the best indicators for assessing whether the person can be protected from infection and disease, although scientists are still working to confirm whether antibody levels can be used as a practical substitute for immune protection.

The research team also assessed the participants’ memory B cells (memory B cells) levels. Such cells can remember pathogens, and if they encounter infectious pathogens they have seen before, they can quickly produce targeted antibodies. Within a month or two after the vaccination, the study participants’ internal memory B cell levels increased by an average of nearly 10 times, and their antibody “titres” or neutralizing antibody levels also surged by about 50 times. These “results” were obvious among previously infected participants, whether they received one or two doses of the vaccine.

In fact, in people without a history of infection, the titers of neutralizing antibodies produced by one dose of vaccine are equal to or higher than the titers produced by two doses of vaccine. The virologist Theodora Hatziioannou, who co-led the research, said it was really amazing. He hopes that everyone’s titer will be like this.

Memory enhancement

The results of Hatziioannou et al. also suggest the biological basis of the effectiveness of a single injection on the infected. For 12 months after the participants were infected, their memory B cells were not static. Instead, these cells took a full year to evolve, which allowed them to make antibodies that are more effective and versatile than those produced immediately after infection.

Other studies have confirmed this idea. Some studies have shown that a single injection can stimulate the growth of antibodies and infection-fighting T cells. John Wherry, an immunologist at the University of Pennsylvania Perelman School of Medicine in Philadelphia, said they all saw almost the same thing. After the COVID-19 infection has recovered, the second dose of the vaccine does not seem to have any effect.

Although most studies on this topic have so far focused on mRNA vaccines, preliminary evidence from studies conducted in the United Kingdom and India shows that if you rely on Oxford-AstraZeneca’s injections, single-dose The strategy may be successful. The injection uses an engineered adenovirus. For example, a study published last month showed that a dose of AstraZeneca’s vaccine produced a much stronger immune response among infected medical staff than among uninfected colleagues. The authors write that these results support a single-dose vaccination strategy for people who have been infected to increase coverage and protect more people.

Stacy Wood, a marketing expert who studies vaccine informatics at North Carolina State University in Raleigh, believes that a single shot policy for those who have been infected may even help overcome people’s indifference to vaccines. She believes that propaganda work that takes full account of personal characteristics is not to create confusion, but to help persuade those who think their own situation is different (including the history of infection). Reducing the number of injections, and all the side effects, anxiety and time that come with it, is also an attractive proposal for some people who are hesitant to vaccinate.

Wood believes that at this point, a more targeted approach may be better.

Increasing evidence has been sufficient to convince many scientists that the precious second dose of vaccine should not be distributed to people who have been infected.

Expanding the role of the second dose of vaccine

Only one dose of vaccine will be provided to those who have been infected with COVID-19, leaving many much-needed doses of vaccine left. With additional vaccines available, there is no need to postpone the second shot of certain populations, as noted in a letter signed by eight COVID-19 scientists published on EBioMedicine in May. Moreover, more and more countries and regions lacking vaccines are following in the footsteps of scientists, at least for young adults whose immune systems are not compromised.

But not all governments agree with this approach. For example, in the United States, where vaccines are relatively abundant, officials still recommend two doses of vaccine for everyone. Kate Grusich, a spokesperson for the US Centers for Disease Control and Prevention in Atlanta, Georgia, said it is not recommended to determine a history of previous infections for the purpose of vaccine decisions.

The scientists also pointed out that some people infected with SARS-CoV-2 have a relatively weak immune response. Wherry said that this reaction is particularly common in asymptomatic COVID-19 infected people. These individuals have a wide range of antibody production and persistence. According to the previous PCR results confirmed infected people and concluded that some people may be missed.

This is where diagnostic antibody testing can help.

Viviana Simon, an infectious disease expert at Mount Sinai and the signatory of the EBioMedicine letter, said that screening for hepatitis B virus antibodies is already a routine practice in some cases to guide vaccination strategies against the infectious disease. This can also be used against SARS-CoV. -2 Spike protein antibody to complete, which is a sign of natural and vaccine-induced immunity.

Simon said that when in doubt, she would support the second injection. But she personally hopes that we will eventually be able to switch to more personalized plans and suggestions.

(source:internet, reference only)

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