Do I need another Covid-19 booster? An epidemiologist answers 3 questions about immunity
Do I need another Covid-19 booster?  An epidemiologist answers 3 questions about immunity

Do I need another Covid-19 booster? An epidemiologist answers 3 questions about immunity

Last in March 2022, U.S. Food and Drug Administration approved another booster shot of Covid-19 vaccines for vulnerable populations in the United States, a step approved by the Centers for Disease Control and Prevention. Persons aged 50 years and older and certain immunocompromised persons who are at higher risk of serious illness, hospitalization and death are entitled to a second booster dose four months after receiving their first booster shot.

Another booster shot is equivalent to the fourth dose for people who received one Pfizer-BioNTech or Modern mRNA series or a third dose to those who received single-shot Johnson & Johnson vaccine.

In Israel, people are in the same vulnerable categories as the United States began receiving the fourth dose in January 2022. Britain recently began administering the fourth dose to humans 75 years and older and invented it a “spring amplifier“In Germany, the over 60 years is now entitled to a fourth shot of the mRNA series.

I’m an epidemiologist University of Texas Health Science Center School of Public Health and Founder and Author of Your local epidemiologist, a newsletter that translates the latest public health science into everyday use.

Recent recommendations have led many to wonder about the importance of boosters for protection against Covid-19. Does the third shot decrease with time? Is a fourth dose needed? What if you have had a previous infection?

After reviewing the growing body of research on how the immune system shifts over time after each dose, it is clear that a different booster for vulnerable populations has a meaningful benefit with very little risk.

The FDA’s authorization allows for an extra booster shot for vulnerable populations, but the agency stopped making it a broad recommendation.

How long does a Covid-19 booster last?

There is clear evidence that a third dose of the mRNA series – or the first booster dose – was and still is essential to ensure a robust immune response against The Omicron variant for all age groups. This is due in part to the immune response decreases with time and also in part because Omicron has been shown to be in part effective in avoiding immunity from existing Covid-19 vaccines and from previous infections.

But then the question becomes: How well does the immunity from the first booster last over time?

The best real-time data to follow on the vaccine’s effectiveness over time is in the UK. The UK Health Safety Agency currently has follow-up data for 15 weeks after the third dose or first booster shot. In his latest report, the effectiveness of vaccines against infection decreases significantly after a third dose. In the UK report, the vaccine efficacy against hospitalization holds up much better compared to the efficacy against infection. But even the protection against hospitalization is slightly declining over time.

Although these data are insightful, 15-week follow-up data are not very useful in the United States because many Americans received their third dose up to 24 weeks ago.

ONE recent study assessed the shelf life of a Moderna third dose after six months. Researchers found declining levels of neutralizing antibodies six months after the booster. CDC also found significant declining protection against the emergency department and emergency visits five months after the first booster. Vaccine efficacy against hospitalization decreased slightly, but remained broadly five months after the booster.

The above studies gathered all age groups. But researchers know that older adults do not have as lasting an immune response as younger people. This explains why breakthrough infections have occurred a lot higher rate among persons aged 65 years and over. A recent study in Lancet assessed the durability of a third dose among people aged 76 to 96 years. Researchers found that the third dose improved neutralizing antibodies, but against Omicron, the antibodies still dropped significantly after a booster.

President Biden gets his second booster image on camera, and Dr. Anthony Fauci discusses the benefits of a booster.

Do we need an extra booster?

Now that Israel has been delivering the fourth dose for several months, researchers have some data to rely on to assess its effectiveness. There are three studies that have been released so far, one of which has not yet been peer-reviewed.

In a study published in New England Journal of Medicineassessed researchers infection rates and serious illness after a fourth dose – or other booster – among more than one million people aged 60 and over in Israel. The researchers found that after a fourth dose, the frequency of Covid-19 infection was twice as low as after a third dose. However, this protection declined rapidly after six weeks. They also found that the incidence of serious illness was four times lower compared to those who received only three doses. However, it is important to note that admissions among both groups were very low.

Important, another study assessed the effectiveness of the fourth dose among younger health professionals in Israel. The results confirmed that the antibody level dropped significantly five months after the third dose. Unfortunately, the efficacy of the fourth dose was not different from the efficacy of the third dose in this population of younger healthcare professionals. In other words, there may not be the meaningful benefit of another booster with the same formula for young, healthy populations.

Researchers conducted a third study, one that has not yet been peer-reviewed, in a major health care system in Israel among people aged 60 to 100 years. Among 563,465 patients in health care, 58 percent received a new booster. During the study period, 92 people who received the second booster died, compared to 232 people who only had the first booster. In other words, the second booster corresponded to a 78 percent reduction in deaths compared to the first booster alone.

What if you got Omicron?

The combination of both being vaccinated and having experienced a Covid-19 infection is called “hybrid immunity.” More than 35 studies has shown that hybrid immunity offers complementary and broad protection. This is because immunity from the vaccines is directed against the tip protein – after which Covid-19 vaccines were designed And infection-induced immunity targets the whole virus more broadly.

So it is not unreasonable to skip another booster if you were infected with Omicron variant. That does not mean people should targeted get SARS-CoV-2, the virus that causes Covid-19. But it is clear that hybrid immunity is a viable path to protection.

In short, there is strong evidence that a fourth dose – or other booster – provides meaningful protection among vulnerable populations, including people over 60. So a second booster is reasonable for some groups.

But while a fourth dose may benefit a select group, it is far more important that people receive their first, second, and third doses.

This article was originally published on The conversation by Katelyn Jetelina at the University of Texas Health Science Center in Houston. Read original article here.

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