The Centers for Disease Control and Prevention endorsed the second booster shot of the COVID-19 vaccine for vulnerable populations in the US after the FDA authorized it.
Four months after receiving the initial booster shot, certain people who are at higher risk for severe disease, hospitalization and death are eligible.
A second booster shot is equivalent to a fourth dose for people who received a single-shot Johnson & Johnson vaccine.
In Israel, people in vulnerable categories began receiving fourth doses. The UK recently started giving a fourth dose to people 75 years and older. Those over 60 years old can now get a fourth shot of the series in Germany.
I am an epidemiologist at the University of Texas Health Science Center School of Public Health and founder and author of Your Local Epidemiologist, a newsletter that summarizes the latest public health science for everyday use.
The latest recommendations have left many wondering about the importance of boosters. Does the third shot fade over time? Is a fourth dose necessary? What if you have had an illness before?
It is clear from the mounting body of research that another booster for vulnerable populations has little to no risk.
There is clear evidence that a third dose of the mRNA series or the first booster dose is critical for ensuring a robust immune response against the omicron variant for all age groups. Omicron has been found to be partially effective at evading immunity from the existing COVID-19 vaccines and from prior infections.
Is immunity from the first booster holding up over time?
The UK has the best real-time data on vaccine effectiveness. The UK Health Security Agency has follow-up data for 15 weeks after the first booster shot.
After a third dose, the effectiveness of vaccines against infections decreases. In the UK report, vaccine effectiveness against hospitalization is holding up better than against infections.
Over time, protection against hospitalization is decreasing. The data is insightful, but 15 weeks of follow-up data is not very helpful in the US because many Americans got their third dose up to 24 weeks ago.
After six months, the Moderna third dose was assessed. Six months after the booster, researchers found waning levels of neutralizing antibodies. Five months after the first booster, the CDC found waning protection against emergency department and urgent care visits.
Five months after the booster, vaccine effectiveness against hospitalization remained the same.
All age groups were pooled in the studies. Older adults don't have the same immune response as younger people. The higher rate of breakthrough infections among people ages 65 and up is explained by this.
A recent study in the Lancet assessed the longevity of a third dose among older people. The third dose improved neutralizing antibodies, but they still dropped after a booster.
Researchers have some data to use to assess the effectiveness of Israel's fourth dose. There are three studies that have been released so far.
Scientists assessed the rates of infections and illness among more than a million older people in Israel in a study published in the New England Journal of Medicine.
The researchers found that the rate of COVID-19 infections was lower after a fourth dose. After six weeks, the protection waned. The rate of severe disease was four times lower when compared to those who only received three doses. The hospitalizations among both groups were very low.
The effectiveness of a fourth dose among health care workers in Israel was assessed. Five months after the third dose, the results confirmed that the levels of antibody dropped.
The effectiveness of the fourth dose was the same as that of the third dose in this population of younger health care workers. The benefit of a second booster of the same formula for young, healthy populations may not be significant.
The third study was done at a large health care system in Israel for people aged 60 to 100 years.
58 percent of patients in the health care system received a second booster. 92 people who received the second booster died compared to 232 people who only had the first booster. The second booster reduced death by 78 percent compared to the first booster alone.
hybrid immunity is a combination of being both vaccine and COVID-19 positive.
More than 35 studies have shown that hybrid immunity is complimentary and broad. This is due to the fact that the vaccines target a spikeprotein after which the COVID-19 vaccines were designed.
It's not unreasonable to skip a second booster with a confirmed infection. This does not mean that people should get the virus that causes COVID-19. It is clear that hybrid immunity is a path to protection.
There is strong evidence that a fourth dose or second booster provides meaningful protection for vulnerable populations, including people over 60. Another booster is reasonable for some groups.
It is more important that people get their first, second and third doses than it is that they get a fourth dose.
The University of Texas Health Science Center at Houston has an assistant professor named Jetelina.
This article is free to use under a Creative Commons license. The original article is worth a read.
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