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Daily Briefing

You're vaccinated and got Covid-19. How much immunity do you now have?


The highly transmissible omicron variant is likely increasing the number of breakthrough infections among the vaccinated as it continues to surge across the United States. And while research suggests these breakthrough infections can significantly increase immunity against future coronavirus infections, many health experts still encourage pandemic precautions post-breakthrough.

Access our new omicron surge toolkit 

How many people have experienced breakthrough infections?

According to data from Johns Hopkins University, at least 20% of Americans—or over 66 million people—have had Covid-19 since the beginning of the pandemic. Of this number, a small portion has been breakthrough cases among those who are vaccinated.

Although it is difficult to quantify the exact number of breakthrough cases that have occurred—largely due to lack of comprehensive tracking—a CDC analysis of 27 states found that 1.8 million breakthrough infections occurred between April and November 2021. Around 96% of these infections occurred after June when the delta variant began spreading in the United States.

Breakthrough infections among the vaccinated were seemingly rare occurrences. According to an ABC News analysis of 36 states, only around 1.37% of those who were fully vaccinated developed a breakthrough infection between January and December 2021. Hospitalizations and deaths from breakthrough infections were similarly low during the same time period at around 0.05% and 0.01%, respectively.

However, since the highly transmissible omicron variant emerged, experts have warned that breakthrough infections are likely to become more common.

"With omicron displaying increased transmissibility, breakthrough cases will unfortunately become even more normalized," said John Brownstein, and epidemiologist at Boston Children's Hospital.

Breakthrough infections boost immunity, but experts still urge caution

Several studies suggest that a combination of vaccine immunity and natural infection can result in a "hybrid immunity" that significantly boosts a person's immune system against the coronavirus. For example, a recent study of vaccinated health care workers who had developed breakthrough infections found they had significantly higher antibody levels compared to a control group that had only been vaccinated.

However, this doesn't mean that people who have had breakthrough infections can simply stop practicing safety precautions. According to several health experts, the level of protection provided by hybrid immunity can vary from person to person and may wane over time.

"Going back to 2019 behavior is a little premature," said Akiko Iwasaki, an immunologist at Yale University. "It's really just playing the lottery, because you don't know how many antibodies you've generated."

Separately, Shane Crotty, a virologist at the La Jolla Institute of Immunology said that, while hybrid immunity is "the best immunity you can get," it's not "a force field that can completely stop [infection from the coronavirus] no matter what."

Health experts have also warned against trying to get infected on purpose to develop hybrid immunity as the coronavirus is unpredictable and can result in severe illness even in young people.

"I really worry that people will intentionally get infected so they can get to this 'new normal,'" said Celine Gounder, an infectious disease specialist at Bellevue Hospital Center. "Something could go wrong, and they could end up in the hospital."

In addition, even with hybrid immunity, people still are at risk of being reinfected and potentially spreading the virus to others, including those who are more vulnerable to severe disease from Covid-19. According to Jennifer Gommerman, an immunologist at the University of Toronto, some vaccinated people who were previously infected with delta have been reinfected with omicron.

"You have to remember there are vulnerable people in the community, and we have to continue to do things like wearing masks," Gounder said. "It's not just about protecting yourself, it's about protecting other people."

However, what recovering from a breakthrough infection can bring to vaccinated people, especially those who are young and otherwise healthy, is "some peace of mind," the New York Times writes, allowing them to live their lives with less fear and worry.

According to Ashish Jha, dean of the Brown University School of Public Health, people who have had breakthrough infections, particularly if they have also been boosted and are not at high risk of severe disease, should feel confident about their level of protection for at least the first three months following the infection.

"Could you get reinfected? Yeah, if somebody in their most contagious moment hacks in your face over and over, maybe," Jha said, but "a normal interaction in a restaurant or a bar" is likely safe. (Mitropoulos, ABC News, 12/21/21; Langmaid, CNN, 1/18; Blum, New York Times, 1/19)


Learn more: Check out our new omicron surge toolkit

We've collected our best resources and insights for creating capacity, supporting staff, communicating with patients, and more. This page will be a consistent work in progress as we compile the newest and most helpful resources. Check out all the resources, including:


Advisory Board's take

What recurrent outbreaks will really mean for health care leaders

Christopher KernsBy Christopher Kerns, Vice President of Executive Insights

The omicron surge is genuinely, even if temporarily, straining the health care system. And if this level of intensity plagues our health care system annually… then 'something’s gotta give,' as they say. Health care workers won't be able to manage through this forever, at least not in the way they have been obliged to do so.

But here's the thing: it’s by no means clear that future Covid-19 surges will look like omicron. While hard to imagine, they could actually be worse. Or, hopefully, they could be significantly milder, a possibility that increases if prior Covid-19 infection continues to protect against future severe illness. Unpredictability is the whole point of genetic mutation, after all. The point is that we just don't know, and it could be harmful to offer prescriptive guidance based on assumptions that may or may not be true and don’t appear to be reinforced with compelling disease models. In fact, prescriptive guidance may only help in areas where political will is strong enough to enforce it, and it is evident that this will (and the associated public willingness to comply) is rapidly dwindling. And I should also note that omicron’s experience shows that even the most restrictive enforcement is little match for a respiratory virus that seems to increase in transmissibility (if not lethality) with new variants.

I think it is important to double down on what this Vox piece only tangentially references—the problem is more about staffing than it is about beds. We've discussed workforce implications when the future is uncertain, and we can confidently discuss supply/demand and how to prepare for the future when we have no idea what is coming. That feels more useful than projecting implications about future winters mimicking this current one.

Our guidance

Rather than basing guidance off uncertain future worst-case scenarios, we believe in preparations that will support the health system regardless of our future situation. Our recommendations to prepare for the future are the same as what we have been saying for two years:

  • Embrace the outpatient shift to make room in hospital beds;
  • Adopt top-of-license care models to efficiently deploy the most appropriate resources; and,
  • Apply scalable tech solutions wherever possible to help make up for what we now have to accept are structural staff shortages.

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