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Boosted Californians Getting COVID At Twice The Rate Of Those Vaccinated But Not Boosted

SACRAMENTO (CBS13) — According to California's current COVID-19 dashboard, people who are boosted are getting the virus at twice the rate of people who are vaccinated but not boosted. Boosted Californians are also being hospitalized with COVID-19 at a higher rate.

To be clear, the data show people who are unvaccinated are still far more likely to get COVID-19 and to be hospitalized. We're talking about the greater risk for people who both are vaccinated and boosted compared to those who are just vaccinated. That's an especially important nuance for the immune-compromised who may have a false sense of security around boosted friends, family, and crowds. 

The State Data

As of Monday, California's COVID-19 dashboard prominently noted that "unvaccinated people were 4.8 times more likely to get COVID-19 than people who received their booster dose."

But what it didn't say, and what the same data indicated, is that during the same time period, boosted people were twice as likely (2.2x) to get COVID-19 as people who are vaccinated but not boosted. They were also more likely (1.75x) to be hospitalized. 

Waning Immunity

"What is going on? What doesn't the data tell us?" CBS13 Investigative Reporter Julie Watts asked UCSF Infectious Disease Specialist, Dr. Phillip Norris.

"Well, the data have to be taken into context, and what we don't know are time and location," Dr. Norris said, adding that for many people, their vaccine boosts are waning.

"So by three months, you've lost a lot of the protection. By six months, it's like you never got boosted," he said.

Data indicates the shift in boosted case rates happened in late February when boosted people went from being less likely to get COVID-19 to more likely to get it than people who are vaccinated but not boosted. 

"Do you think that's because, for most people, the boost started to wear off?" Watts asked.

"I do," Dr. Norris said. "And the other part of the equation is if someone didn't get boosted in the first Omicron wave, they were also more likely to get infected."

Hybrid "Super Immunity"

"And study after study is showing that...hybrid immunity, getting vaccinated and having a natural infection, is far stronger protection against cases and hospitalizations than either being vaccinated and boosted alone or having a natural infection alone," added Dr. Monica Ghandi, an infectious diseases expert with UCSF.

Both noted that, as a result, highly populated areas where more people are boosted — like the San Francisco Bay Area — may be skewing the state data. Bay Area case rates are currently double the state average.

"California and the Bay Area, in particular, have been more locked down than other regions," Dr. Ghandi said. "And that's why you're seeing swelling of cases."

"So it looks like the boost is causing this infection,"  Dr. Norris said, "but really it's where you live and when the boost was given, that really clouds those data."

Boosted Hospitalizations 

Dr. Norris added that it's not surprising to see that boosted Californians are more likely to be hospitalized because higher-risk populations are more likely to get boosted. 

"So a healthy 20-year-old is less likely to get boosted than an unhealthy 70-year-old who has cancer at the same time," he said. Even with a boost, compromised individuals are still more likely to have more severe COVID outcomes.

Both note that it is still important for the immunocompromised to stay boosted. They just shouldn't have a false sense of security around others who are boosted.

Keeping Boost Data Quiet 

"This seems to be important information. Why isn't anyone talking about this data?" Watts asked.

"You know, there seems to have been a policy in this country to not acknowledge how protective natural immunity is," Dr. Ghandi said.

CBS13 asked the California Department of Public Health (CDPH) why it hadn't publicized the trend in an effort to protect immunocompromised individuals who may have a false sense of security around other boosted friends, family, and crowds.

The agency would not answer our specific questions.

Instead, CDPH sent a lengthy response touting the benefits of vaccines (included at the end of the article).

As of Monday, the most recent available data was from April 24. CDPH would not comment on whether the trend has continued over the past three weeks.


While it appears that boosted individuals are more likely to get COVID right now than those who are vaccinated but not boosted, it is important to point out that getting boosted doesn't make you more likely to get COVID.

"It's a good thing to be boosted if you're older. It's a good thing to be boosted," Dr. Ghandi said. "It's just that natural immunity plus vaccine is the strongest protection that you can get."

But Norris adds, "That does not mean we should go out and try to get infected because you always face the risk of having a bad outcome. But for those who've had both vaccine and infection, they probably have stronger antibody responses."

Statement provided by an unnamed representative of CDPH on May 17th: 

COVID-19 vaccines are safe and have been shown to protect against severe illnesses, hospitalizations and death due to COVID-19.  Vaccines also protect against infections, but this protection wanes over time.  The research shows that boosters further enhance or restore protection that might have waned over time after a COVID-19 primary vaccination series. People are protected best from severe COVID-19 illness when they stay up to date with their COVID-19 vaccines, which includes a booster for many people.  A second booster is recommended for some persons at higher risk of more severe disease. 

CDPH and the CDC have been tracking the risk of infection, hospitalization and death for unvaccinated persons, persons who have received a primary vaccine series and persons who have received a booster dose.  These data have consistently shown a protective effect of COVID-19 vaccines and boosters.  These data are derived from surveillance data and not from studies specifically designed to measure vaccine effectiveness.  At this point in the pandemic, several factors make these surveillance data less useful for this purpose.  Unvaccinated persons, persons who have had a primary series only, and persons who have had a booster may now have different levels of prior infection and different testing practices.  Also, vaccination timing is increasingly important and accounting for vaccination timing is difficult with surveillance data.   

The CDC has also recognized these difficulties and has posted a notice on their website:  CDC COVID Data Tracker: Rates of COVID-19 Cases and Deaths by Vaccination Status

Nonetheless, other types of data show the benefits of COVID-19 vaccination and booster doses as recommended.  CDC has summarized other types of studies showing vaccine effectiveness here:  CDC COVID Data Tracker: Vaccine Effectiveness

Boosters remain the best way to prevent hospitalization and death from COVID-19 for our most vulnerable, and CDPH recommends that everyone stay up to date on their COVID-19 vaccinations. 

Thank you,

California Department of Public Health

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