The Food and Drug Administration’s highest-ranking vaccine official Tuesday said that Americans may need to get another Covid booster shot in fall because public health officials expect people to have less immunity and the transmission of the virus will increase during the colder months.

Head of the FDA’s vaccine safety office, Dr. Peter Marks indicated that the U.S. may need to provide fourth shots for those under 50 years old in the Fall. People who are now eligible for fourth shotsMarks said that Marks could likely be granted a fifth chance if the evidence is compelling.

Marks suggested that the U.S. could use a new vaccine to target a specific Covid type or mix of multiple Covid varieties. Current vaccines are designed to protect against the original strain of the virus, which emerged in Wuhan in China late 2019. Their effectiveness has decreased over the years as the virus evolves. Moderna and Pfizer are currently conducting clinical trials for shots to target both the omicron variant and any other circulating variations.

On April 6, the FDA will host an advisory committee meeting to discuss booster shots and update vaccines to provide better protection from variants.

Marks stated that it would not surprise if people need an extra booster to be able to take advantage of a general booster campaign. It is possible that instead of using the current vaccines, which are known as vaccines against the prototype viruses, we may decide to move on to vaccines that either protect against one variant or another.

Tuesday’s FDA approval granted a fourth dose to Moderna and Pfizer of the original vaccine, which is for those 50+. For people aged 12 and under with impaired immune systems, the FDA approved a second booster. Pfizer eligibility is for people 12 and older who have certain underlying medical conditions. Moderna eligibility is for those aged 18 or older with similar health issues.

Marks stated that evidence in Israel shows that a fourth dose may be able to reduce hospitalizations and deaths among older adults. BA.2, a more deadly subvariant of the omicron omicron, has introduced new wave after wave of infection to major European countries as well as China. This subvariant has become the dominant one in the U.S. White House Chief Medical Advisor Dr. Anthony Fauci stated earlier in the month that BA.2 might cause an increase in infections in the U.S. but he doesn’t expect another spike.

Marks explained that FDA offered a fourth dose for older adults, and an additional shot to individuals with compromised immune system to help them protect themselves from any future wave of flu in the U.S.

Public health professionals and scientists are split on whether boosters should be added. Israeli researchers found that four shots of boosters significantly decreased mortality among people over 60 compared with those who had received three. This study by Clalit Health Services and Ben Gurion University, Israel’s biggest health-care provider has not been peer reviewed.

A study in Israel of 18-year-old health care workers showed that the fourth dose of immunity did not increase immunity. Many of these individuals still had mild to moderate breakthrough infections and were symptomatic.

In a letter sent to The New England Journal of Medicine, Dr. Gili RegevYochay wrote that “a fourth vaccination of young healthy health-care workers may only have marginal benefits.”