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Experts say booster doses of the COVID-19 vaccine should not be administered too close together. Mario Tama/Getty Images
  • Regulators in Europe say getting too many COVID-19 booster shots may actually weaken your immune response.
  • Scientists in Israel also reported that a fourth vaccine dose doesn’t appear to produce enough antibodies to protect against an Omicron variant infection.
  • Experts explain that our bodies need time to process the stimulation from a vaccine or infection.
  • They recommend that people still practice safety protocols such as mask-wearing and physical distancing even if they are fully vaccinated.

European regulators say giving COVID-19 booster shots too frequently may weaken immune response.

At a press briefing, experts from the European Medicines Agency (EMA) argued that COVID-19 booster shots should not be given too close together.

“We are rather concerned about a strategy that entangles repeated vaccination within a short term. We cannot really continuously give a booster dose every 3 or 4 months,” Marco Cavaleri, the head of Biological Health Threats and Vaccines Strategy at the EMA, said at the briefing.

“If we have a strategy in which we give boosters, let’s say every 4 months approximately, we will end up potentially having a problem with the immune response, and the immune response may end up not being as good as we would like it to be. So we should be careful in not overloading the immune system with repeated immunization,” Cavaleri added.

In addition, researchers in Israel say a fourth COVID-19 shot doesn’t appear to produce enough antibodies to prevent infection from the Omicron variant.

This comes as Israel is offering a fourth dose of COVID-19 vaccination to those who work in healthcare and people who are over age 60.

Dr. William Schaffner, an expert in infectious diseases at Vanderbilt University in Tennessee, says it is crucial to give the immune system time to process what it receives in the initial vaccination series.

“It’s just well established that the immune system needs some time to process the information that it gets: the stimulus from a vaccine or a natural infection. And then if you want to boost it, you have to give it a certain amount of time to ‘digest’ that information so that it can respond optimally,” Schaffner told Healthline.

“For example, the traditional hepatitis B vaccine is given as a three-dose series,” he explained. “The first two doses are given a month apart, and then you wait 6 months, or even later, you could wait 2 years. And then the immune system, when it’s stimulated by that third dose, will respond. But you don’t want to give that third dose before 6 months. It’s a little bit counterintuitive, but the immune system often needs some time to process this new information, and in effect, train its troops to respond optimally to that booster dose.”

The Centers for Disease Control and Prevention (CDC) recommends that everyone over age 12 who received the Pfizer vaccination in the initial vaccination series get a booster at least 5 months after their second dose.

Those 18 years and older who received the Moderna vaccination in the initial series should get a booster at least 5 months after completing the initial series.

Adults who received the single dose Johnson and Johnson vaccination should get a booster at least 2 months following their vaccination.

In early January, the CDC issued guidelines stating that those who are moderately or severely immunocompromised and have difficulty retaining immunity should get a booster and additional primary shot, for a total of 4 shots. That extra dose is recommended to be at least 5 months after a third shot.

“In the case of Israel, they’re trying to build a very robust population-level immunity to, in essence, eliminate COVID-19 as a problem. The question is… is it not enough with a third dose, the booster dose?” Dr. Edward C. Jones-Lopez, an assistant professor of clinical medicine at Keck School of Medicine of USC, told Healthline.

“It’s really about public health authorities trying to understand which is the best strategy here to try and get us out of this mess. Israel has the means to do it,” he said. “They have a relatively small number of people that they can… implement this in an easier way, let’s say compared to other large, somewhat more chaotic countries like the U.S. and some countries in Europe and so on. Each country is pushing, in their own way… trying to get out of this mess.”

Dr. Otto O. Yang, an infectious disease expert at the University of California Los Angeles, says the four-shot offering occurring in Israel may be a good idea.

“Based on the fact that immunity against this virus seems intrinsically short-lived, which is why immunity from the vaccines is short-lived, this is probably a good idea. The fact that the virus has evolved into Omicron is what has sped up the need for boosters — the antibodies against the vaccine are targeted against the original strain, and so much higher levers are needed against Omicron,” Yang told Healthline.

“If the vaccines were adapted against Delta and Omicron, immunity would last much longer because lower levels of antibodies would be needed since those antibodies are directly targeted against those variants,” he added.

Even with vaccinations and boosters, the risk of spreading COVID-19 to others remains.

The CDC recommends that anyone over age 2 who is not vaccinated wear a mask in indoor public areas. Those vaccinated should wear a mask indoors in public in areas of high transmission.

Masks are required for everyone on planes and public transport.

It is also recommended that you stay at least 6 feet away from other people in public.

“On the societal level, Delta and especially Omicron have made breakthrough infections common in vaccinated persons, which means they can be contagious,” Yang said.

“Getting infected, even if you are personally protected, lets the virus continue to circulate and infect people who may die…. perhaps your elderly family member, or a friend who has a kidney transplant in whom the vaccine is not effective. Your not getting infected protects all the people along the chain of transmission from you who could get sick and die,” he noted.