Coronavirus: How long can vaccine protect?

Coronavirus: How long can vaccine protect?

How long can the protective effect of the new coronavirus vaccine last? With the first group of vaccinated people nearly four months after the initial vaccination, this issue has become more and more important.

In short, the answer is: we haven’t fully figured it out yet. But more and more data are providing us with clues in this regard. The following is what we have so far.

##How long is the protection period of the vaccine? Will effectiveness diminish over time?

Recent data from Pfizer shows that the protective effect of the vaccine can last at least six months. The results of the study show that the level of antibody decline during this period is very small. The vaccine produced by Pfizer is one of the three vaccines currently available on the US market. According to a study published recently in the New England Journal of Medicine, the antibodies in Moderna vaccine recipients remained at high levels more than six months later.

University of Pennsylvania professor of microbiology Scott Hensley (Scott Hensley) said that some people mistakenly believe that this means that those vaccines can only provide six months of protection. “This view is wrong.” Dr. Hansley said. “We only have six months of data… in another six months, we might know that the vaccine’s validity period can reach One year.”

##How does the protective mechanism of the vaccine work?

Deepta Bhattacharya, an associate professor of immunobiology at the University of Arizona in Tucson, pointed out that because the immune system has many levels, the new crown vaccine may be able to at least play a role in a long time. Some degree of protection.

Both Pfizer and Moderna’s vaccines require two injections, and the first dose of vaccine can provide a sufficient degree of protection. Batachaya said that the second dose of the vaccine increased the level of antibodies and T cells produced by the body. T cell is a type of white blood cell that can destroy cells infected by the virus. “Even if the effectiveness of protection drops a lot, it can still play a protective role.” He said.

##Are Johnson & Johnson vaccines as long-lasting as Pfizer and Moderna vaccines?

Johnson & Johnson’s vaccines use different technology platforms. They have not been available for a long time, and relevant data are not yet available.

In the period from two weeks after vaccination to 70 days, the antibody level of Johnson & Johnson vaccine vaccinators seems to show a rising trend. Therefore, despite reports that the effectiveness of Johnson & Johnson’s vaccine is not as good as that of Pfizer and Moderna, Dr. Batachaya pointed out that at a later point in time, its effectiveness may reach a level similar to that of the latter two vaccines.

##Can vaccines provide lifelong immunity?

Some scientists believe that the vaccine may have a certain degree of protection for several years or even decades, but we do not know the specific situation.

Monica Gandhi, a professor of medicine at the University of California, San Francisco and an infectious disease doctor, pointed out that a 2020 study in the journal Nature found that SARS patients were sick After 17 years, the T cells in the body are still playing an immune role. SARS is also known as severe acute respiratory syndrome (SARS). The coronavirus that causes it is similar to the coronavirus that causes new coronary pneumonia.

Dr. Gandhi pointed out that even if the antibody level drops, according to the evidence presented in a new preprint article, seven weeks after receiving the Pfizer vaccine, the vaccine produced memory B cells in the vaccinated person. This is also a type of white blood cell that can produce new antibodies in a stimulated state decades later. A 2008 study in the journal Nature found that when survivors of the 1918 influenza pandemic were exposed to the same influenza strain 90 years later, their memory B cells could also produce antibodies.

##Will the emergence of mutant viruses affect the duration of vaccine protection?

This is difficult to predict.

So far, against most known mutant viruses, vaccines seem to provide good protection. But as the virus continues to mutate, more powerful variants may appear, and they are more likely to bypass the line of defense built by vaccines. Bata Jaya said that this variant may already exist, but it has not been discovered and has not been sequenced. He pointed out, “If they already exist, then as we get closer to herd immunity, these variants will face (adaptive evolution) selective pressure in expanding the rate of viral infection.”

Hansley said that in this situation, antibody levels become very important. Vaccines using messenger RNA technology usually provoke higher levels of antibodies than those after natural infection. Hansley said that even if a mutation prevents certain antibodies from binding to the virus, they can still provide a certain degree of protection because the vaccine produces a large number of antibodies. But how strong this protective effect is and how long it can last, we don’t know.

##What happens if a mutant virus reduces the effectiveness of the vaccine?

Ann Sheehy, an immunologist and virologist at the College of the Holy Cross in Worcester, Massachusetts, points out that the immune system, if not invulnerable, is not vulnerable. A mutant virus may weaken, but will not completely eliminate the protective effect of the vaccine.

If someone is still infected with the new coronavirus after being vaccinated, the condition may not be that serious. “The immune system is very smart, and when you encounter such a problem for the second time, you can usually cope better.” Shee said.

##Is it necessary to strengthen the injection?

In response to some new virus variants, pharmaceutical companies are racing to test the effect of enhanced injection.

David Topham, a professor of microbiology and immunology at the University of Rochester Medical Center, said, “In view of the fact that some people’s immunity declines are indeed worse than others, it’s out of caution. Careful consideration”, at least the next few years may need to strengthen the needle.

Some experts point out that the need for enhanced needles may last longer, especially if there are a large number of virus variants.

Compared with the seasonal coronavirus that causes the common cold, the major difference between the coronavirus that causes new coronary pneumonia and the former is that the new coronavirus can replicate anywhere in the body. Topham said that seasonal coronaviruses generally only replicate in the respiratory tract. Whether it is possible that the new coronavirus will eventually cause only mild illness like other common coronaviruses, or whether it will continue to cause serious illness if the booster is not injected every year. The answer to these questions is still unclear.

##After the second dose of the vaccine, I had no side effects, but my husband had side effects. Does this mean that the vaccine protects him better than me?

it’s not true. Scientists usually say that side effects are a good thing. Dr. Shee pointed out that this shows that your immune system is working.

“After the vaccine is injected into the body, it will make your immune system aware that you have been exposed to foreign substances.” Shee said, “If someone feels uncomfortable, it means they have a strong immune response.”

But the reverse is not true. Shee said, “Just because you have no symptoms of discomfort, it does not mean that you have not developed a strong immune response.”

##After natural infection, can the vaccine still have a protective effect?

The Centers for Disease Control and Prevention recommends that even if you have been infected with the new crown virus, you should get the new crown vaccine. Although there is evidence that natural infection can produce a strong protective effect, the specific situation varies from person to person.

A study by Lancet Microbe found that there are differences in the immune response between people. Some people’s antibodies disappear within three months, while some people’s antibody levels are eight. It is still very high after a month.

“I think in reality, everyone’s situation is different.” Dr. Topham said. “It is critical to ensure that a good immune response can be generated from the start.”