How Effective Were Vaccines During the Omicron Surge?

vaccines vs omicron variant

Verywell Health / Jessica Olah

Key Takeaways

  • COVID-19 vaccines remained highly effective at preventing severe disease and death amid Omicron, according to new CDC studies. 
  • Unvaccinated adults were more likely to be hospitalized compared to fully vaccinated and boosted adults. 
  • Infectious disease experts believe vaccine effectiveness can apply to BA.2 and potentially future variants as well.

The COVID-19 mRNA vaccines remained highly effective at preventing severe disease and death from infection during the Omicron surge in January, according to new studies published by the Centers for Disease Control and Prevention (CDC). 

While some people worried that protection would wane over time and vaccines would not be as effective against the Omicron variant, recent data from the CDC shows just how effective vaccines were.

In fact, as Omicron became the dominant variant, the CDC found the vaccine was 79% effective in preventing death or the need for mechanical ventilation for people who received the initial two doses of an mRNA vaccine from either Pfizer or Moderna. Protection was even greater (94%) for people who received a booster shot (three mRNA vaccines) during that same time period. 

“While vaccines are less effective against general infection by Omicron compared to other variants, they still tend to retain their protection against severe disease and death,” Jorge Salinas, MD, assistant professor of medicine and infectious diseases at Stanford University, told Verywell. “So it shouldn’t surprise anyone that a report shows that vaccines including boosters help prevent severe disease, the need for hospitalization and mortality.”

A second CDC study found that while hospitalizations were up for all adults in January 2022, unvaccinated adults who became infected were 12 times more likely to be hospitalized compared to those who were vaccinated with two doses. Adults who had received the primary series of vaccines, but who hadn’t received a booster, were three times more likely to be admitted to a hospital compared to adults who also received a booster shot.

The first CDC study looked at vaccine effectiveness against the Alpha, Delta, and Omicron variants using data reported at 21 hospitals across 18 states between March 21 and January 24, 2021. The second study collected data on adult patients who were hospitalized in 99 counties across 14 states from July 1, 2021, to January 31, 2022.

Even though the Omicron variant led to an increase in cases, hospitalizations, and deaths this winter. these CDC findings provide support and confidence that vaccines and booster shots do prevent COVID-19’s most serious outcomes, James Hay, PhD, infectious disease epidemiologist at the Harvard T.H. Chan School of Public Health, told Verywell.

“The concern over Omicron is that the virus has changed quite a bit compared to previous variants, so some parts of the immune system that were previously trained to recognize SARS-CoV-2 no longer do. But that doesn’t mean that everything has stopped working,” Hay said. “We still have cells and antibodies, which are generated by getting vaccinated, that can attack the Omicron variant. What this means is that although our immune systems aren’t quite as good at stopping us from getting infected in the first place, they are still really good at stopping the virus from causing severe illness.”

Vaccines Provide Protection Against Severe Disease

According to Tony Moody, MD, associate professor in the department of immunology at Duke University, vaccines, in general, are designed to prevent severe disease, not to prevent infection. He explained vaccines do this by training the immune system to recognize and respond to disease-causing organisms. This allows the immune system to respond efficiently and effectively, minimizing any severe damage caused by the disease.

“People may still become infected, but when they do, their immune system response results in less damage to healthy tissue, leading to less signs and symptoms of disease,” Moody said. “Although the Omicron variant had a spike protein that was different from the vaccine strain, there were enough similarities between them to allow the immune system to recognize the infection. This is very similar to what happened with earlier waves of variants and it is likely to apply to future variants as well.”

Hay added that while it takes the body a little bit more time to figure out how to deal with new variants than it would with existing variants, like Alpha or Delta, immunity is still being generated against the new variant because of previous vaccines.

“Our immune system is really good at adapting to the tools that it already has—this is why getting vaccinated is useful even if we get new variants—our immune system can take its original tools and quickly adapt them, and add to them, to deal with new variants,” Hay said. “By giving our immune systems a head start on dealing with Omicron, that buys our immune systems enough time to build the right tools and fight off the infection.”

Both Hay and Moody explained boosters also play crucial roles in reducing severe disease and death by providing additional training to the immune system, raising antibody levels, and allowing people to be even more efficient at dealing with the infection when it occurs.

What Does This Mean for BA.2?

While concerns are growing over a new variant called BA.2, which is a close relative of the Omicron variant, infectious disease specialists believe our vaccines will continue to provide good protection against serious disease, hospitalizations, and death.

“We believe that the vaccines will have similar efficacy against BA.2, though it is important to remember that we are seeing these data in real-time and predicting the future is challenging at best and impossible at worst,” Moody said. “Present data suggest that BA.2 is slightly more transmissible than BA.1 and that the incubation period between exposure and shedding is slightly shorter. If anything, these characteristics argue more strongly for vaccination, since vaccination is one of the things that might contribute to reducing shedding and transmission events.”

Sharon Nachman, MD, Chief of the Division of Pediatric Infectious Diseases at Stony Brook Children’s Hospital, told Verywell via email that while vaccines will continue to do their job at preventing hospitalizations and death from potential new variants, the virus especially BA.2 is contagious and will be able to spread very quickly and cause infection, something people need to be vigilant about.

However, Salinas added more research is needed to tell whether protection against severe disease and other serious outcomes from the infection will last for years or whether it will wane in the wake of new variants that may develop in the future.

What This Means For You

The CDC found vaccines are highly effective at protecting against severe infection and disease from the Omicron variant. Health experts recommend getting vaccinated and boosted to prevent worse outcomes of infection for potential new variants.  

Other Important Considerations

According to the experts, vaccines are still the best way to protect yourself and vulnerable people around you who may be susceptible. Getting boosted prompts the immune system to raise antibody levels which makes a difference between having a mild infection and being at risk for something more severe.

“Vaccines work and remain one of the key things we can do to protect people from severe disease and death from this pathogen,” Moody said. “Are they perfect? No, but no medical intervention is. Are they effective? Absolutely, and that’s what these studies show.”

Salinas and other health experts advise people to follow the CDC and Food and Drug Administration (FDA) guidance on additional doses or boosters that may be needed in the future.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Taylor CA, Whitaker M, Anglin O, et al. COVID-19–associated hospitalizations among adults during SARS-CoV-2 Delta and Omicron variant predominance, by race/ethnicity and vaccination status — COVID-NET, 14 states, July 2021–January 2022. MMWR Morb Mortal Wkly Rep. 2022;71(12);466–473. doi:10.15585/mmwr.mm7112e2

  3. Iuliano AD, Brunkard JM, Boehmer TK, et al. Trends in disease severity and health care utilization during the early Omicron variant period compared with previous SARS-CoV-2 high transmission periods — United States, December 2020–January 2022. MMWR Morb Mortal Wkly Rep. 2022;71(4):146-152. doi:10.15585/mmwr.mm7104e4

  4. World Health Organization. Statement on Omicron sublineage BA.2.

By Alyssa Hui
Alyssa Hui is a St. Louis-based health and science news writer. She was the 2020 recipient of the Midwest Broadcast Journalists Association Jack Shelley Award.