Reasons for not needing the 4th Covid-19 vaccine shot yet

Both Pfizer and Moderna are asking the US government for authorization to administer dosesCovid-19 vaccineWednesday.

Last week, Pfizer announced it had applied to the US Food and Drug Administration (FDA) for emergency use authorization for an additional booster dose for adults 65 years of age and older.

Pfizer CEO Albert Bourla says Americans should get a Covid-19 vaccine every year, just like they get a flu shot in the fall.

“Right now, the third shot is still protective against hospitalization and death,” Mr. Bourla said. However, he highlighted concerns that the protection would not last long.

Moderna also said it has applied for authorization of a fourth dose of its vaccine for all adults, allowing health care providers to determine the appropriate use of the booster dose by considering factors such as a person's age and underlying medical conditions.

However, according to infectious disease experts, giving a fourth dose to people in the US may not be appropriate.

The virus has changed, the vaccine remains the same

The current vaccines from Moderna and Pfizer still follow the original formula, which has not been adjusted to match the circulating variants, such as Omicron and the fast-spreading sub-variant of Omicron, BA.2.

The Prime Minister has repeatedly directed to prepare all conditions for vaccinating children. Photo: Archive

All of those vaccines were developed based on the virus that was decoded in Wuhan in January 2020. Over the past two years, the virus has evolved but the vaccine has not.

“I don’t think pharmaceutical companies should be talking about booster doses with existing vaccines,” said Dr. James Hildreth, a leading infectious disease expert. “I want to focus on looking at the sequences that are emerging from the variants and trying to make a vaccine that can protect against them, rather than just giving people a fourth dose.”

Dr. Hildreth worries that continuing to use shots tailored to a 2-year-old virus could create new problems. A booster shot with an outdated shot could create antibodies that are less valuable against circulating strains. Or, as the virus evolves, it could learn to develop better resistance to the vaccine.

In addition to working on additional doses for each variant, some independent groups and pharmaceutical companies are also developing vaccines that target different strains of the virus at once, hoping to achieve broad immunity against future variants. However, such a universal vaccine is at least several years away.

There is no data yet that the fourth dose is good for most people.

The available data on the fourth dose of vaccine only show benefit in older people and those with underlying health conditions. There is no data to suggest that booster shots are superior to the immune systems of young, healthy people in preventing severe disease.

A recent study by the US Centers for Disease Control and Prevention (CDC) found that the vaccine was 88% effective at preventing severe complications like ventilator-related illness and death during the peak of the Omicron wave with two doses and 94% effective with three doses, suggesting that a booster shot only provides a small improvement in vaccine effectiveness for most people.

According to another CDC analysis, more than 96% of fully vaccinated people hospitalized with Covid-19 during the Omicron outbreak had underlying health conditions. The same was true for 9 out of 10 booster-vaccinated adults hospitalized with Omicron.

Even Moderna's leadership agrees that fourth-dose programs, at this point, should focus on high-risk patients.

Moderna President Stephen Hoge said that for people with cancer, Covid-19 can be a life-threatening disease, even after vaccination. But he said a fourth dose is not necessary for people under 65 with no underlying health conditions.