Need a second booster shot?Epidemiologists have several answers

US Food and Drug Administration in late March 2022 Approve the second booster shot Development of COVID-19 vaccine for vulnerable populations in the United States Immediately after approval According to the Centers for Disease Control and Prevention. People over the age of 50, and certain immunocompromised people at high risk of severe illness, hospitalization, or death, are eligible four months after receiving the first boost.

The second booster shot is Pfizer-BioNTech or Modern RNA series Or a third dose for the recipient Single Johnson & Johnson Vaccine..

In Israel, people in these same vulnerable categories Started receiving the 4th dose In January 2022.The UK recently started a fourth dose for people 75 years old and over And call it “Spring booster.. In Germany, they are 60 years old and over Currently targeted for the 4th shot of the mRNA series.

I am an epidemiologist Center for Health Sciences, University of Texas Faculty of Public Health and Founders and Authors Your local epidemiologistA newsletter that translates the latest public health sciences for daily use.

The latest recommendations leave many questions about the importance of boosters for protection against COVID-19. Did the third shot fade over time? Do I need a fourth dose? What if I have been infected before?

After reviewing an increasing number of studies on how the immune system changes over time after each dose, it is clear that another booster for the vulnerable population will bring significant benefits with little risk.

Vaccine efficacy after first booster immunization

There is clear evidence A third or first booster dose of the mRNA series is important and still important to ensure a strong immune response to. Omicron variant For all age groups.This is partly due to the immune response Decline over time Also, in part, Omicron has proven to be partially effective in evading immunity from existing COVID-19 vaccines and previous infections.

But the problem is: How long will the immunity from the first booster last over time?

The best real-time data for tracking vaccine efficacy over time is in the United Kingdom. The UK Health and Security Agency currently has follow-up data for 15 weeks after the third dose or the first booster immunization. In the latest report, The effectiveness of the vaccine against infection is significantly reduced after the third dose. In the UK report, the effectiveness of the vaccine for hospitalization is far superior to that for infection. But even protection against hospitalization has declined slightly over time. This data is insightful, but 15-week follow-up data is not very useful in the United States. This is because many Americans received a third dose 24 weeks ago.

A Recent research The durability of the third dose of Moderna after 6 months was evaluated. Researchers found that levels of neutralizing antibodies were reduced 6 months after booster immunization. CDC Also, important decline protection was found For emergency and emergency treatment visits 5 months after the first boost. The effectiveness of the vaccine for hospitalization was slightly reduced, but remained largely maintained 5 months after booster immunization.

The above studies pooled all age groups. However, researchers know that older people do not initiate a more durable immune response than younger people.This explains why breakthrough infections are so common. Higher rate Among people over 65 years old.Recent research on lancets Evaluated the durability of the third dose Among people between the ages of 76 and 96. Researchers found that the third dose improved the neutralizing antibody, but even in the face of Omicron, the antibody was significantly reduced after the booster.

2nd booster dose / 4th shot data

Now that Israel has given it a fourth dose for several months, researchers have some reliable data to assess its efficacy. There are three studies published so far, one of which has not yet been peer-reviewed.

In a study published in the New England Journal of Medicine, scientists Infection rate and serious illness after the 4th dose – Or a second booster – among more than 1 million people over the age of 60 in Israel. Researchers found that after the fourth dose, the COVID-19 infection rate was half that after the third dose. However, this protection soon diminished after six weeks. They also found that the incidence of severe illness was one-fourth that of those who received only three doses. However, it is important to note that hospitalizations in both groups were very low.

The important thing is Another study We evaluated the efficacy of the fourth dose among young Israeli healthcare workers. As a result, it was confirmed that the antibody level decreased significantly 5 months after the third administration. Unfortunately, the efficacy of the fourth dose was no different from the efficacy of the third dose in this population of young healthcare professionals. In other words, for a young and healthy population, there may not be a meaningful benefit to a second booster with the same prescription.

Researchers conducted a third study Things that haven’t been peer-reviewed yetIn Israel’s large medical system, between people aged 60 to 100. Of the 563,465 patients in the healthcare system, 58% received a second boost. During the study period, 92 people who received the second booster died, compared to 232 who had only the first booster. In other words, the second booster corresponds to a 78% reduction in deaths compared to the first booster alone.

What happens if Omicron is infected with COVID-19?

The combination of experiencing both vaccination and COVID-19 infection is “Hybrid immunity.. ” is more than 35 studies It shows that hybrid immunity offers complementary and wide-ranging protection. This is because immunity from the vaccine targets peplomer. COVID-19 vaccine was designed – Infectious immunity is more broadly targeted at the virus as a whole.

Therefore, it is not unreasonable to skip the second booster with confirmed Omicron infection. This does not mean that people need to deliberately acquire the virus that causes SARS-CoV-2, COVID-19. But it’s clear that hybrid immunity is a viable path to protection.

In short, there is strong evidence that a fourth dose (or a second booster) provides meaningful protection among vulnerable populations, including people over the age of 60. Therefore, another booster immunization is reasonable for some groups. And while the fourth dose may benefit the selected group, it is much more important for people to receive the first, second and third doses.

Caitlin JeterinaAssistant Professor of Epidemiology, University of Texas Health Sciences Center

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