Three years into the Covid-19 pandemic, few Americans are rolling up their sleeves to get a Covid vaccine. 

Only 15.7% of U.S. adults had received the newest Covid shots from Pfizer, Moderna and Novavax as of Nov. 18, according to the latest data from the Centers for Disease Control and Prevention. Those jabs, some of which won approval in mid-September, are designed to target the omicron subvariant XBB.1.5.  

“Here’s the bottom line: COVID-19 vaccine uptake is lower than we’d like to see, and most people will be without the added protection that can reduce the severity of COVID-19,” the CDC wrote in an update on its website last week. 

Some vaccine makers and health experts believe U.S. Covid vaccination rates in 2024 and beyond will likely look similar to the meager uptake of the latest round of shots this fall and winter.

The bigger uncertainty appears to be whether rates could increase down the line — and what would cause more people to roll up their sleeves.

Some experts hope a new, more convenient slate of shots targeting more than one respiratory virus could boost Covid vaccinations. But others are more skeptical about whether those combination jabs will make a difference. 

Experts and vaccine makers can agree that low Covid vaccination rates are concerning, even as cases of the virus dwindle from their pandemic highs. 

Vaccines remain a critical tool to protect people from death or hospitalization from Covid, which is still killing Americans every day. Fewer jabs could leave many people — especially older adults and those with underlying medical conditions — vulnerable to severe infections. 

Lower vaccination rates also make the U.S. less prepared if a new, more concerning variant of the virus emerges and fuels another surge in cases and hospitalizations, added Dr. Ali Mokdad, an epidemiologist and chief strategy officer for population health at the University of Washington. 

Covid shot uptake has dwindled since the first vaccines against the virus rolled out in late 2020, when Americans felt more urgency to protect themselves as cases soared. 

This year, roughly half of adults who were previously vaccinated said a lack of worry about Covid is a reason why they haven’t gotten a new vaccine, including a quarter who called it a “major reason,” according to a poll released earlier this month by health policy research organization KFF. 

That reasoning reflects multiple factors. First, Covid infections haven’t spiked significantly in the U.S. this year, especially compared to prior years of the pandemic, according to Mokdad. 

He added that people have more immunity from previous vaccinations or infections, which protects them from getting severely ill from the virus. Data also suggests that omicron variants, which are the dominant Covid strains circulating in the U.S., tend to be less severe than some previous variants, Mokdad added.

“People are like, ‘I got that, it didn’t really hurt me. So why do I need to go and get a vaccine?'” Mokdad said.

Nearly 4 in 10 adults also said they have been too busy to get the new Covid shot, according to the KFF poll. 

Some Americans may not be used to treating their Covid vaccination as a “routine activity” for their health every year, according to Jennifer Kates, senior vice president of KFF.

Others may not be prioritizing Covid shots because they are confused about their risk levels and the benefits they will personally see from another booster, added Dr. Brad Pollock, chair of UC Davis Health’s department of public health sciences.

What’s more, a group of Americans may never get Covid vaccines because they remain skeptical about their safety and efficacy.

Political polarization has exacerbated that effect: Republicans have grown increasingly hostile toward the shots, and some have even fueled conspiracy theories and disinformation about getting vaccinated.

Only 23% of Republican respondents to KFF’s poll said they had or would get the latest Covid shot this fall or winter, compared to 40% of independents and 74% of Democrats. 

The lack of urgency around Covid could weigh on uptake in the coming years, said Dr. Nicole Iovine, chief hospital epidemiologist and an infectious disease physician at the University of Florida.

But she noted that the people who receive the new Covid vaccine this fall will likely get future iterations. “There’s definitely a core of people who are going to always get their vaccine,” said Iovine.

Jefferies analyst Michael Yee specifically noted that patients who are at high risk of severe Covid and are open to vaccination “would be reasonable” to take it each year. 

Most Covid vaccine makers themselves assume that uptake in 2024 and beyond could look similar to what the U.S. sees this fall and winter. 

“So, we are assuming that things will be the same in the years to come, Covid fatigue, anti-vaccination rates, so the people that did it this year will continue doing it next year,” Pfizer CEO Albert Bourla said during a call with investors in mid-October. “I think it is a quite safe assumption.”

Similarly, Moderna assumes that everyone who got their Covid booster in 2023 will “at least” get a Covid shot in 2024 and beyond, Moderna Chief Commercial Officer Arpa Garay said during the company’s third-quarter earnings call last month. Garay also said the company expects about 50 million Americans to get a new vaccine between September and December this year.

Novavax Chief Operating Officer John Trizzino told CNBC that there’s “a logic and reality” to Pfizer and Moderna’s outlooks. But he said 2023 won’t be “100% indicative” of what vaccination rates in the future could be, especially since the rollout this year was an “adjustment period” to the commercial market with delays in distribution.

Trizzino also said combination shots targeting Covid and other viruses, including one from Novavax, will likely enter the market in a few years, which could increase Covid vaccinations in the U.S. 

“I think that it actually will help. More Americans get a combined flu and Covid shot, which should increase the number of people that get a Covid vaccine over time because it’s much more easy from a convenience perspective for anybody, as well as the technician to administer,” Moderna CFO Jamey Mock said in an interview earlier this month.

But other experts are more skeptical about whether those jabs will have a notable effect.

All three companies are developing vaccines targeting different combinations of Covid, flu and respiratory syncytial virus, which collectively strained the U.S. health-care system last winter and could continue to peak around the same time each year. 

The companies have released positive midstage trial data on some of their combination shots this year and expect their jabs to win approval from U.S. regulators in 2025 and 2026. 

Combination jabs are nothing new: Childhood vaccines have long been combined to eliminate additional trips to the doctor’s office and reduce the number of injections a patient needs to get during their visit. That approach can lead to fewer missed shots and higher vaccination rates for diseases they target, according to Andrew Pekosz, a professor at the Johns Hopkins Bloomberg School of Public Health. 

Other studies also argue that a combination jab targeting Covid and the flu in particular could boost Covid vaccination rates, which lag behind flu shot uptake this year. 

More people are used to receiving flu vaccines annually, so they may “find it easier to replicate such health action in the case of a combination shot” targeting Covid and the flu, according to a 2023 study that analyzed 30 different papers on the vaccine approach. 

However, Iovine of the University of Florida doesn’t believe combination shots will have a significant effect on Covid vaccination rates.

While the jabs may be attractive for people who already get their shots or those who are looking for more convenient vaccination options, they may do little to change the minds of people who are avoiding a Covid vaccine for reasons such as skepticism or concerns about safety and efficacy.

Jefferies analyst Yee similarly said he doesn’t believe the “advantage of convenience would be the differentiating factor” determining whether someone gets a Covid vaccine, which is why combination shots may not “materially change uptake.”

He added that some people are still worried about whether combination vaccines cause more side effects than stand-alone shots do. Pfizer, Moderna and Novavax haven’t flagged notable differences between the side effects of their combination vaccines and existing shots, but more data is needed.

The FDA and CDC are hoping to transition toward a flu shot-like model for Covid vaccines, meaning people will get a single jab every year that is updated annually to target the latest variant expected to circulate in the fall and winter. 

But advisors to the FDA have raised concerns about shifting to yearly Covid vaccines, noting that it’s unclear if the virus is seasonal like the flu. Kates added that establishing a more annualized approach to Covid vaccination in the minds of Americans “will take time.”

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