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Booster shot effectiveness and mixing different types of vaccines are among the new developments in the COVID-19 pandemic. Jon Cherry/Getty Images
  • There’s an array of new information about the effectiveness of COVID-19 vaccines and strategies, in particular involving the Omicron variant.
  • Pfizer officials say their booster shot appears to be effective against this latest coronavirus variant.
  • Some studies also indicate that mixing vaccine type when getting a booster shot might also offer strong protection.
  • Pfizer officials say they hope to have a vaccine designed specifically for the Omicron variant available by March.
  • Experts say you shouldn’t wait to get a booster. They urge you to get vaccinated as soon as you are eligible.

It might be a challenge to keep up with all the news surrounding COVID-19 vaccines.

There’s new information about mixing different types of vaccines, how effective booster shots are, and what could be coming our way in the near future.

Here’s a look at some of the latest developments.

A Pfizer-BioNTech booster shot may be effective in protecting against the Omicron variant.

Pfizer has released results from an initial laboratory study indicating that a third dose of its COVID-19 vaccine increases antibodies by 25-fold against the Omicron variant compared with just two doses.

“Although two doses of the vaccine may still offer protection against severe disease caused by the Omicron strain, it’s clear from these preliminary data that protection is improved with a third dose of our vaccine,” Albert Bourla, the chairman and CEO of Pfizer, said in a statement.

Dr. Dean A. Blumberg, the chief of pediatric infectious diseases at the University of California, Davis, said the study from Pfizer is promising news.

“What it shows is we can overcome the viral resistance to immunity by increasing the antibody titers,” Blumberg told Healthline.

An antibody titer is the level of antibodies found in the blood. Antibodies are molecules the immune system makes that help protect the body from the coronavirus.

“I haven’t seen any data from Moderna, but I fully expect it to be very similar to the Pfizer vaccine. Anybody who’s got either the Pfizer or Moderna vaccine, I feel confident these results apply to them,” Blumberg said.

The Omicron variant is regarded as a “variant of concern” by the World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC).

A variant of concern is one in which there’s evidence of more severe disease, an increase in transmissibility, or a reduction in neutralization by antibodies gained via a previous infection or vaccination.

“It appears to be more infectious, more transmissible than the previous strains. The studies from South Africa show that it’s rising in an exponential manner in terms of the proportion of infections that it’s causing,” Blumberg said.

“Some of the studies suggest that it may be twice as infectious as Delta, and we all know what happened in the U.S. when Delta started becoming the predominant strain, starting in the late spring and early summer, that’s when we had a big surge of infections. So, the same thing may happen with Omicron,” he added.

Vaccination remains the most important public health measure to protect against COVID-19.

Pfizer officials report that the first two doses of their vaccine are 70 percent effective in preventing hospitalizations from the Omicron variant.

The CDC still recommends adults get a booster shot either 2 months after their Johnson & Johnson (J&J) one-dose vaccine or 6 months after their second Pfizer-BioNTech or Moderna shot.

Adults can choose any vaccine as their booster, regardless of what vaccine they have already received.

Dr. William Schaffner, an infectious disease expert at Vanderbilt University in Tennessee, said those who have received the J&J vaccine would benefit from receiving a booster with either Pfizer-BioNTech or Moderna.

“We know J&J doesn’t produce… nearly as much antibody. And it doesn’t have very long duration in comparison to the mRNA vaccines,” Schaffner told Healthline. “That’s why we recommend that people… who had received J&J vaccine get an mRNA booster.”

A number of studies suggest that mixing vaccines from different manufacturers during the first two doses produces a better immune response.

Given this, Blumberg suggests those who have had Pfizer-BioNTech in their initial series might consider choosing Moderna for their booster where possible.

By the same token, those who have had Moderna for their initial series might consider Pfizer-BioNTech as their booster if these alternatives are readily available.

When it comes to booster effectiveness, experts say the mRNA vaccines are likely to produce similar results, with Moderna potentially providing slightly more protection.

“There is an increasing number of studies that suggest the Moderna vaccine results in a higher antibody titer compared to Pfizer, a slightly higher antibody titer. Both mRNA vaccines appear to be significantly better than Johnson & Johnson, and the Moderna appears to be slightly better compared to Pfizer in terms of inducing higher titers,” Blumberg said.

Pfizer officials say they are continuing to develop an Omicron-specific vaccine and hope to have it available in March.

However, Schaffner said people shouldn’t delay getting their booster for the sake of waiting for a specific vaccine.

“I’m always concerned that a vaccine deferred is often a vaccine never received. If you spend too much time looking for the other vaccine, you may put it off indefinitely,” he said.

The proportion of the population who have yet to receive their initial COVID-19 vaccine, he said, is also still a cause for concern.

“We in the United States still have a large proportion of the population, adults and recently children, who remain unvaccinated,” Schaffner noted. “They will continue to drive our pandemic here. Well over 90 percent of patients being admitted to hospital continue to be unvaccinated. So, that part of the equation is one that continues to be challenging, and we haven’t solved yet.”

Blumberg argues those who choose to wait for an Omicron-specific vaccine may find that by the time it’s available, a new variant has emerged.

“There have been so many things we’ve been unable to predict with COVID, trying to think that you can think five steps ahead, I think, is just not going to be realistic,” he said.

“If it’s been 6 months since your original vaccination, I would encourage people to be vaccinated, get that booster. That will keep you safer, it will [help] prevent infection, and will also help prevent infection among your close contacts, your household loved ones,” Blumberg added.