Do I really need to get a COVID-19 booster? CDC real-world study confirms effectiveness

The Centers for Disease Control and Prevention released a study Friday that provided real-world U.S. numbers about the effectiveness of boosters for both the delta and omicron variants of COVID-19.

The study analyzed cases from 383 emergency departments and urgent care clinics and 259 hospitals across 10 states from Aug. 26 to Jan. 5. It looked only at people 18 and older.

The study found that mRNA vaccines made by Pfizer and Moderna have waning effectiveness 180 days after the second dose. The effectiveness went from 94% to 82% for keeping people out of the emergency room and urgent care and from 94% to 90% for people keeping people from being hospitalized. 

The study also showed the difference in effectiveness during delta compared with omicron and how boosters played a role once they were introduced in the fall. During delta, vaccine effectiveness against emergency room and urgent care visits went from 86% between two weeks and six months after the second dose to 76% after six months. Two weeks or more after a third dose, the effectiveness went to 94%. 

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For hospitalizations during delta, the effectiveness was 90% in the first six months after two doses, 81% six months after dose two and 94% after the third dose.

With omicron, that effectiveness against urgent care and emergency room visits went from 52% within six months of the second dose to 38% six months after the second dose to 82% after the booster. 

For hospitalizations during omicron, those numbers went from 81% within six months of the second dose to 57% six months after dose two to 90% after the third dose.

"It is great news," said Dr. Manjusha Gaglani, director of the Center for Research in Vaccines and Infections and chief of pediatric infectious diseases at Baylor Scott & White Health. Getting boosted is working, she said, and this study really points out the necessity for doing so. 

People who are unvaccinated or have not been boosted six months after receiving the vaccine are "the most at-risk right now," Gaglani said. "We should just go ahead and get the booster."

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When to get booster

The Food and Drug Administration and the CDC now recommend that people ages 12 and up get a booster shot five months after they received their second Pfizer or Moderna vaccine. The booster for Johnson & Johnson comes two months after that vaccine, which was originally considered a one-dose vaccine. 

People do not need to get the same vaccine for their booster dose. For Pfizer and Johnson & Johnson, the booster is the same dose as the initial one. For Moderna, the booster is a half dose. 

People considered immune compromised were able to start getting a third shot in August, before boosters were recommended for all adults. Those third doses are not considered a booster. Five months after that third dose, they can get a booster.

"Those people are the highest priority if it's been five months since their third dose," Gaglani said. "We want them to keep up with the best protection they can have." 

Since people began getting boosters, there have not been any new safety concerns, she said. The only people who should not get a booster are those who had a severe reaction to the vaccine or are allergic to the vaccine components, which are common in other vaccines.

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Rethinking effectiveness

When the vaccines first came out, effectiveness was measured by infection rates and breakthrough cases. Now we're really thinking about the vaccine as being effective against hospitalization and emergency room visits. 

"The focus is not coming to the ED and overwhelming the hospital system," Gaglani said.

Getting the booster is also important to try to prevent another variant and be able to return to a more normal life. 

"Right now the burden of infection is so high that the virus is in control," she said. "We need to get boosted and give the virus less chance of mutating. We have fallen behind the curve."

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In Austin last week, 681 people were hospitalized for COVID-19, including 152 in ICUs and 68 on ventilators. We saw our highest number of people hospitalized during the pandemic and the highest seven-day average of new hospitalizations since the pandemic began. 

While omicron's spread might help us reach more herd immunity, "it's costing people's lives. It's causing a lot of really sick hospitalized illnesses, including in children. We're not in a good place," Gaglani said.

The hope is that with vaccination and keeping up with boosters, we can get COVID-19 to a place where it becomes seasonal with a vaccine to prevent deaths. 

"When we have control of it like the flu season, we live with it as we go," she said.