Who might benefit from a 4th shot — and who might not

Staff volunteers queue to receive a fourth dose of the Pfizer COVID-19 vaccine at Sheba Medical Center in Israel on December 27, 2021, as the hospital conducts a trial of a fourth jab of the vaccine.

Jack Guez/AFP via Getty Images

One thing that is clear about the Pandemic is that the COVID-19 vaccines are not going to stop the coronaviruses or provide long-term protection from infections.

After the third shot, the booster's antibodies rise up quickly. They begin to decline about a month later. Three months later, the protection against infections drops to 50%.

Should you get a fourth dose of protection?

The answer is likely no, according to a preliminary study published last Tuesday.

Not a third dose, not a fourth dose, not a fifth dose will do anything to stop infections, says Dr. Gili Regev-Yochay, an infectious disease specialist at Sheba Medical Center in Tel HaShomer, Israel.

It is not to say that an additional dose is pointless. An extra dose may be needed for older people or people at high risk. I have seen preliminary data looking into that question.

What does a fourth dose do to the immune system?

About 300 health care workers were given a fourth shot, either Pfizer or Moderna, in the new study. They looked to see if those people were less likely to get sick while working at Sheba Medical Center, compared with health care workers who only got three shots.

The health care workers had their blood tested before and after the fourth dose.

The extra shot boosted the levels of antibodies, but it didn't translate into strong protection against infections. The extra dose reduced the risk of infections by up to 30%. About 20% of the people who received the extra shot became infectious with the omicron variant of the coronaviruses, compared with 25% of the people who received only three shots. T cells are critical for clearing out future infections and the extra dose didn't appear to do that.

The fourth dose restores some protection lost after the third shot, but it doesn't boost immunity beyond that.

Scientists don't know why the fourth dose didn't spark a strong immune response, but some think the current vaccine isn't the best way to fight omicron.

The vaccines being administered are designed to fight different types of infections in 2020.

I think we are just reaching a threshold with this vaccine, says a University of Chicago immunologist.

In my opinion, Omicron has changed everything. The vaccine that worked for previous versions, such as alpha and even delta, is not going to be needed for omicron because this virus is more likely to cause an infection.

The current vaccines give great protection against severe disease by triggering a strong immune response inside the blood. The vaccine does not produce a strong immune response inside the respiratory tract.

She says she is excited that people are working on vaccines that will train the immune system in our lungs to protect us.

Could a fourth dose help extend protection against severe disease?

The current crop of vaccines is still helpful when it comes to saving lives despite the disappointing results for a fourth shot. The vaccines are doing a good job in preventing hospitalizations and death.

Two months after the last dose, a study found that three doses offer protection against hospitalization with an omicron infection. The Morbidity and Mortality Weekly Report reported that the protection drops to 80% after four months.

Some scientists are concerned about a small drop in protection.

According to the MMWR study, protection against severe disease remains higher than against infection, but evidence is emerging that protection against omicron may decline with time.

For people under the age of 65, the waning protection may not cause a big problem because they have a relatively low risk of hospitalization.

If you have an overall higher risk of hospitalization, this waning might cause a bigger impact than if you have a low risk of severe disease.

People with compromised immune systems and people with health factors that increase their risk are likely to benefit from an extra booster.

Akiko Iwasaki, an immunologist at Yale University, says that these people will likely be the first to need another booster.

She says scientists don't know when these people will need the extra shot. We will have to wait and see.

The FDA doesn't have enough data to recommend an extra booster shot for everyone.

Several countries are moving forward with a fourth dose. Sweden began to offer jabs to people over the age of 80 in nursing homes on Tuesday. Anyone over the age of 55 who had their third dose more than five months ago can now get a fourth dose. Israel allows fourth shots to adults over age 60 with underlying health conditions.

It is important for vulnerable populations to get a fourth dose, says Regev-Yochay.