Why boosted Americans seem to be getting more COVID infections

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As COVID-19 cases began to accelerate again this spring, federal data suggests the rate of breakthrough COVID infections in April was worse in boosted Americans compared to unboosted Americans — though rates of deaths and hospitalizations remained the lowest among the boosted.

The new data do not mean booster shots are somehow increasing the risk. Ongoing studies continue providing strong evidence that booster shots offer additional protection against infection, severe diseases, and death.

Instead, the shift underscores the growing complexity of measuring vaccine effectiveness at this stage of the pandemic. This comes as officials weigh key decisions regarding booster shots and pandemic surveillance, including whether or not to use the “crude cases rates”.

It also serves to illustrate a tricky reality facing health authorities amid the latest COVID-19 wave: even many boosted Americans are vulnerable to catching and spreading the virus, at a time when officials are wary of reimposing pandemic measures like mask requirements.

“During this Omicron wave, we’re seeing an increased number of mild infections — at-home type of infections, the inconvenient, having a cold, being off work, not great but not the end of the world. These Omicron variants can break through antibody protection and cause mild infections,” John Moore, a professor at Weill Cornell Medical College of microbiology, explained to CBS News.

“Another dynamic is that people believe they are more protected after vaccinations and boosting. This leads to them taking on more risks,” he stated. “I believe that this is the main driver of these statistics. “

On the CDC’s dashboard, which is updated monthly, the agency acknowledges several “factors likely affect crude case rates by vaccination and booster dose status, making interpretation of recent trends difficult. “

The page was created by the CDC several months ago in response to federal demands for better tracking of breakthrough cases. It has now grown to encompass data from immunization records and positive COVID-19 tests from 30 health departments across the country

For the week of April 23, it said the rate of COVID-19 infections among boosted Americans was 119 cases per 100,000 people. This was twice the rate of infection in people who had been vaccinated, but only a fraction of those who had not been vaccinated.

This could be because there is a higher prevalence of previous infections among people who are not vaccinated or boosted, according to the CDC. There may be an increase in boosted Americans who have stopped wearing masks and other preventive measures, which could lead to an increase in cases.

Some boosted Americans might be more likely to seek out a lab test for COVID-19, as opposed to relying on over-the-counter rapid tests that go largely unreported to health authorities.

“Home testing is, I believe, the single greatest concern in developed nations that can interfere with us measurements,” Ruth Link-Gelles, CDC, told a conference held by the National Foundation for Infectious Diseases.

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Some federal officials have floated the possibility of adopting a survey — similar to those relied on by authorities in the United Kingdom — as an alternative way to track a “ground truth” in COVID-19 cases, though plans to stand up such a system do not appear imminent.

“Moving beyond this crisis, I do think the future is in random sampling. And that’s an area that we’re looking at closely,” Caitlin Rivers, a top official on the agency’s disease forecasting team, told an event hosted by the National Academies last week.

Meanwhile, federal officials are also preparing for key decisions on future COVID-19 vaccine shots, which might up the odds that additional shots might be able to fend off infections from the latest variants.

In the short term, CDC Director Dr. Rochelle Walensky recently told reporters that her agency was in talks with the Food and Drug Administration about extending the option for second boosters to more adults.

Right now, only adults 50 and over and some immunocompromised Americans are eligible to receive a fourth dose.

Next generation of vaccines and boosters

Further down the road, a panel of the Food and Drug Administration’s outside vaccine advisers is scheduled to meet later this month to weigh data from new booster candidates produced by Pfizer and BioNTech as well as Moderna.

BioNTech executives told investors last month that regulators had asked to see data for both shots specifically adapted for the Omicron variant in addition to “bivalent vaccines,” which target a blend of mutations.

Those new vaccines would take about three months to manufacture, the White House’s top COVID-19 official Dr. Ashish Jha told reporters.

“It’s a little bit of a challenge here because we don’t know how much further the virus will evolve over the next few months, but we have no choice because if we want to produce the hundreds of millions of doses that need to be available for a booster campaign, we have to start at risk in the early July timeframe or even somewhat sooner,” Dr. Peter Marks, the FDA’s top vaccines official, said at a recent webinar hosted by the American Medical Association.

Marks stated that bivalent shots were likely to be preferred, due to the possibility of unforeseen variants.

Vaccines that might offer even better “mucosal immunity” – actually fighting off the virus where it first infects the respiratory system – are still a ways off, Marks cautioned.

“I think that we are in a transition time and I, again, will speak openly to the fact that 2022 to 2023 is a year where we have to plan for trying to minimize the effect of COVID-19 with the tools that we have in hand,” Marks said at a recent event with the National Foundation for Infectious Diseases.

“I do believe that, potentially by the 2023-2024 season, we’ll start to see second generation SARS-CoV-2 vaccines,” he added later.

Alexander Tin

CBS News reporter covering pandemics and public health.

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