Health

Controversy ‘should be vaccinated against Covid every 6 months’


Some scientists believe that the annual Covid-19 vaccine should be administered, while others consider this an expensive, unstable and ineffective strategy in the long run.

A year ago, experts and the community believed that two doses of Pfizer, Moderna, AstraZeneca vaccines or one dose of Johnson & Johnson were enough to prevent Covid-19 infection. To date, when the Omicron strain has spread rapidly, Israel has pioneered the fourth dose of vaccine for the vulnerable population. On January 5, the US Centers for Disease Control and Prevention (CDC) approved the third dose of Covid-19 vaccine for a group of teenagers. The agency avoids using the phrase “fully vaccinated” to refer to anyone, as two doses of the vaccine do not appear to be enough to fight Covid-19.

Instead, a person’s immunization status is “enhanced” or “unboosted”. Many Americans therefore wonder: When will this vaccination day end? Should I get a booster shot every few months?

Due to the continuous development of nCoV, scientists no longer want to predict the future of the pandemic. But in recent interviews, dozens of experts have said that whatever happens, it’s unrealistic to try to get a Covid-19 vaccine every few months. This strategy also doesn’t make much scientific sense.

Professor Andrew Pollard, AstraZeneca vaccine researcher, said that universal vaccination every 4 to 6 months is expensive and ineffective. He also noted the need to target vulnerable people instead of mass-injecting everyone 12 years of age and older. According to him, countries should collect more data to determine “whether this population needs additional injections, when and how often.”

“The world has a precedent for routine vaccinations, but I think there are better methods than getting vaccinated every six months,” said Akiko Iwasaki, an immunologist at Yale University. Other strategies, she said, could “save the world from needing booster shots for the rest of their lives”.

According to her, it is very difficult to convince people to line up every few months. About 73% of American adults are fully immunized. But to date, just over a third of those have opted for booster shots.

Like Professor Pollard, Deepta Bhattacharya, an immunologist at the University of Arizona, said: “This doesn’t seem like a sustainable, long-term strategy.” In addition, there are no clinical data demonstrating the efficacy of a fourth dose of vaccine. Repeat vaccination may increase antibody levels, prevent nCoV infection, thereby reducing pressure on the health system. In the context of the spread of the Omicron strain, this expert said that Americans should get the third dose as soon as possible.

However, many preliminary studies show that immunity in users continues to decline several weeks after the third dose. Even with the highest antibody concentrations, booster injections are unlikely to completely prevent Omicron, a strain that can evade immunity.

“It’s very difficult to stop the virus for long. The virus has evolved much better than before. Maybe an Omicron-specific vaccine will be more needed,” said Shane Crotty, a virologist at the Institute of Immunology. La Jolla of California, commented.

Pfizer-BioNTech, Moderna and Johnson & Johnson are all testing the vaccine, which is expected to launch in the coming months. Ali Ellebedy, an immunologist at the University of Washington, said: “If I were to get a fourth dose, I would definitely wait for a specific vaccine against Omicron.”

An elderly man gets his fourth dose of the vaccine at a nursing home in Petah Tikva, Israel. Photo: AP

According to experts, if the goal is to strengthen immunity against Omicron and future strains, the new vaccine will be much better than the vaccine designed based on the original version of nCoV, which appeared two years ago. . Several research groups are developing universal vaccines against corona in general, targeting the non-evolving or very slowly changing parts of the virus.

The next suggestion is to combine existing vaccines with new generation oral or nasal spray vaccines, which better prevent infection because they promote the production of antibodies on the nasal surface and upper respiratory mucosa. This is the first entry point of nCoV.

Scientists say should increase the time between vaccine doses. This is a lesson learned from the fight against epidemics in the past. Initially, many experts opposed the idea of ​​booster injections. Some believe the initial vaccine regimen is effective enough to prevent hospitalizations and deaths. Others say it’s unfair for rich countries to stock up on vaccines for their annual booster shots, especially since many countries don’t have enough of the first dose.

But this perspective changed Omicron appeared and spread non-stop around the globe. “The mutation really changed my mind on this,” said Scott Hensley, an immunologist at the University of Pennsylvania.

He and many of his colleagues now advocate a third dose of vaccination. But they think that countries should not deploy dose 4 like Israel. According to Hensley, other components of the immune system such as T cells and B cells are able to stably fight the virus after three doses, even after only two doses.

Immune cells can’t prevent infection, but they help reduce morbidity and mortality and keep hospitalizations low. “The vaccinated people have milder symptoms when they are hospitalized,” said Michel Nussenzweig, an immunologist at Rockefeller University in New York. He added that Omicron has demonstrated that the world needs to get rid of the goal of preventing all nCoV infections.

According to scientists, in the new phase of the pandemic, The biggest task is to reduce the hospitalization rate. Last fall, Dr. Anthony S. Fauci, the US anti-epidemic adviser, repeatedly mentioned the importance of preventing symptomatic infections. But in recent days, he believes that reducing hospitalizations is really important.

To prevent infection, it is necessary to calculate the correct timing of booster injections based on the prevalence of the strain in the community. For example, many people who get their third shot in early fall are susceptible to Omicron infection because immunity has dropped.

Experts recommend that people get a flu shot right before winter. If Covid-19 outbreaks are seasonal, people may need a booster dose before winter every year, Dr. Hensley said.

Thuc Linh (Follow NY Times)

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