Fourth dose of COVID-19 vaccine: doctors recommend it, but scientists are skeptical
Countries are starting to offer a fourth dose of the Covid-19 vaccine to vulnerable groups, but healthcare professionals are unsure if it will benefit the wider population, reports CNBC.
The U.S. Food and Drug Administration has so far only authorized a fourth shot for people aged 50 and over, and those who are immunocompromised. And the US Centers for Disease Control and Prevention has been skeptical about the need for a fourth dose for healthy adults in the absence of a clearer public health strategy.
These decisions come after an Israeli study showed that while the fourth dose of the Pfizer-BioNTech vaccine provides protection against disease for at least six weeks after vaccination, it provides only short-term protection against infection, which wears off after just four weeks.
So far there is no "good evidence"
The medical consensus so far is that not enough research has been done on what protection a fourth dose might offer.
The World Health Organization has not made an official recommendation for a fourth dose, and "there is currently no strong evidence" that it would be beneficial, WHO Chief Scientist Soumya Swaminathan said.
“We know from immunology that if you give another booster dose, you will see a temporary increase in neutralizing antibodies. But we have also seen that these neutralizing antibodies will decrease quite quickly,” Swaminathan said.
“It happened after the third dose. And it happened again after the fourth dose,” she added.
Paul Goepfert, professor of medicine at the University of Alabama, shares this view, saying that "the fourth dose didn't really do much."
As a study in Israel shows that a fourth dose may provide protection against the disease, countries such as Israel, Denmark and Singapore have made a second boost available to high-risk groups.
“Instead of saying that the protection is waning, I would say that this increased effect is most visible shortly after the introduction of the vaccine, but in general it remains just protective,” said Ashley St. John, assistant professor at Duke-NUS Medical School.
“What is important is that protection against the virus is not weakened, which is the most important effect of vaccination that we are striving to achieve,” she added.
Questions are being raised about the need for additional vaccinations as the emergence of more Covid variants may require more targeted vaccines.
Anthony Fauci, the White House's chief medical adviser, said in January that people may need to get booster shots every year or two.
However, blanket vaccine approaches may not be effective.
It is possible that high-risk groups, such as the elderly, may need to be vaccinated annually, Swaminathan said. But "it is unclear whether a healthy adult would need a regular annual vaccination."
It's also important to note that current vaccines may not work for future variants of Covid-19, she said.
If the virus "changes so much that you need to change the composition of the vaccine, then you won't need another shot," Swaminathan added. “The problem with changing the composition of a vaccine is that you are always playing catch-up.”
Göpfert said "only time will tell" how long the population should be boostered, but the safest approach would be to "schedule a booster every year and possibly combine it with a flu vaccine."
The WHO announced that weekly Covid deaths have fallen to their lowest level since March 2020.
But the more contagious subvariant omicron BA.2 remains the dominant strain in the US, accounting for 68,1% of all cases in the country in the week ending April 23, according to the CDC.
Although experts predict that the BA.2 sub-variant is unlikely to be more dangerous than the original Omicron strain, it should be cause for concern.
“I really think the infections will continue. They covered most of the country,” Goepfert said. “But as for the severe forms of the disease, I think that there will be fewer and fewer of them.”
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St. John said that patients from places with adequate vaccination coverage would only be exposed to "mild or manageable disease" and this would reduce "the burden on the healthcare system.
“Just like preparing for an exam, a booster vaccine can trigger immune system memories and improve performance during a real test,” she added.
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