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Previously vaccinated adults in the U.S. who have not received the bivalent COVID-19 booster vaccine were often unaware they were eligible, didn't know it was available, or thought they already had immunity, according to survey data from the CDC.

Of more than 1,100 respondents who had received at least two prior doses and responded to an initial survey in early November 2022, 62.1% had not received the bivalent booster. When asked why they did not get it, 23.2% said they were unaware they were eligible, 19.3% said they didn't know where or that it was available, and 18.9% said they thought they already had immunity against infection, reported Alyssa H. Sinclair, MA, of Duke University in Durham, North Carolina, and colleagues.

After being provided with eligibility and availability information, 67.8% of respondents who had not received the bivalent booster said they would, Sinclair and team noted in the .

"To help increase bivalent booster coverage, healthcare professionals and public health practitioners should use evidence-based strategies to convey information about booster vaccination recommendations and waning immunity, in addition to increasing convenient access to vaccination," they wrote.

When the researchers followed up with these individuals 1 month later, 28.6% reported that they had received the booster. Of the remaining individuals who had not yet gotten it but had said they would, 82.6% still intended to do so. Those who had not received the booster most commonly reported being too busy, forgetting, or worrying about side effects.

"Reminders from providers and trusted messengers, accommodations (e.g., time off work to recover), and convenient access (e.g., at workplaces, schools, or shopping centers) might motivate persons to act on their intentions," Sinclair and team noted.

In the survey, respondents were broken down into age groups. Among the 18-39 and 40-59 age groups, lack of awareness about eligibility and vaccine availability were commonly cited reasons for not receiving the booster.

Of note, among those in the 40-59 and 60-and-over groups who said they had not received the booster because they were already protected against infection or severe disease due to previous vaccination or infection, nearly three-quarters had not experienced a SARS-CoV-2 infection or received a COVID-19 vaccine within the preceding 6 months, "and more than one half had never been infected."

Given that both vaccine effectiveness and infection-conferred immunity wanes, and viral variants are continually evolving, "these participants likely overestimated their protection," Sinclair and team noted. "An online intervention has been shown to correct inaccurate estimation of COVID-19 exposure risk; similar strategies could correct misconceptions about the need for COVID-19 bivalent booster vaccination, such as interactive online tools that provide personalized immunity estimates."

Side effects and safety were most likely to be of concern in the 60-and-over group. The researchers suggested that these concerns could be addressed by disseminating emerging safety and effectiveness data related to bivalent booster vaccination through providers and public health messengers.

The survey was conducted in November to December 2022, when bivalent booster uptake in the U.S. was at 12.1% for adults. As of January 4, Sinclair and team said coverage still remains low, at 18.2% for adults. "Increasing bivalent booster vaccination coverage will require a multifaceted approach to address reasons for non-vaccination," they wrote.

U.S. adults 65 and older have the highest rate of bivalent booster vaccination (39.6%), according to the , and recent data out of Israel among this age group demonstrated 81% effectiveness against COVID-related hospitalization with the updated booster.

The survey was conducted using Prolific, an online survey platform. Participants received $1 for completing the 3-5 minute survey and another $1 for completing a 1.5-minute follow-up survey.

Of the participants, 65.4% were white, and 51.9% were women. Most (95.8%) of the initial 1,200 survey participants had received two or more COVID-19 vaccine doses. Participants who had received only one dose or were unsure if they had received a bivalent booster dose were excluded from further analyses.

Of the 396 survey respondents who had received the bivalent booster, their main reasons for doing so included to protect themselves (90.7%), to prevent severe disease (80.6%), and to protect others (75.0%).

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