Reported reasons adults had not received a bivalent COVID-19 booster dose differed across age groups.
The only constant of the COVID-19 pandemic is change.
We have moved through periods of no therapeutics, to highly effective vaccines and antivirals, to treatments rendered ineffective by the newest variants. Now, the US Centers for Disease Control and Prevention (CDC) estimates 49.1% of new COVID-19 infections are caused by the Omicron subvariant XBB.1.5.
Bivalent mRNA COVID-19 boosters are the newest effort to counteract the virus’s mutations. Moderna and Pfizer-BioNTech both have received authorization for their bivalent boosters, designed to protect against the ancestral and Omicron BA.4/BA.5 variants.
The CDC first recommended a bivalent booster vaccine for persons 12 years and older on September 1, 2022. However, relatively few eligible US adults have received the recommended bivalent booster. In their new Morbidity and Mortality Weekly Report(MMWR), the CDC looked for explanations for this low uptake.
The investigators conducted an opt-in internet survey of 1200 US adults. The participants had all received at least 1 dose of a COVID-19 vaccine. Included participants were all US residents, fluent in English, and at least 18 years of age.
Data were collected from an initial survey, administered November 1-5, 2022, and from a follow-up survey, administered December 6-10, 2022. The investigators utilized quota sampling to recruit approximately equal proportions of adults aged 18-39, 40-59, and 60 and older. The sample was not representative of race or ethnicity, as the vast majority of prospective participants identified as non-Hispanic White.
Respondents reported dates of all previous confirmed COVID-19 infections, if any. They also indicated if they had received any COVID-19 vaccinations. The participants who had received a bivalent COVID-19 vaccine could select all applicable reasons for their decision, as well as add their own.
Similarly, the participants who opted not to get a bivalent booster could select or add all the reasons for their decision. After indicating why they had not received a bivalent booster, respondents were shown information about bivalent booster vaccine eligibility and availability. They then reported whether, after reading the information, they planned to receive a bivalent booster dose. Participants who had not initially received a bivalent booster were sent a follow-up survey a month later to gauge whether they had decided to get the shot.
The included 1200 participants were divided relatively evenly across the 3 age groups. Approximately 65.4% were White, and 51.9% were women. Although 95.8% of respondents had received 2 or more COVID-19 vaccine doses, only 34.4% (n = 396) had received a bivalent booster dose.
Of the 396 participants who had received a bivalent booster, these were their most reported reasons for doing so: 90.7% got the booster to protect themselves, 80.6% to prevent severe disease, and 75.0% to protect others. These top reasons were consistent across the 3 age groups.
Interestingly, reasons reported by the 714 participants who had not received a bivalent booster differed by age group. Among the adults 18-39 years old, 29.8% reported they were not aware of their eligibility, 23.5% were unaware updated booster doses were available, and 18.4% believed they still had strong protection against COVID-19 infection.
Among adults 40-59 years old, 22.1% were unaware they were eligible for a bivalent booster, 21.3% believed they still had strong protection against severe disease, and 18.5% believed they still had strong protection against COVID-19 infection.
Finally, among the adults 60 years and older, 20.2% believed they still had strong protection against infection, 17.5% were concerned about side effects, and 16.1% were unsure whether the bivalent booster was effective.
It is notable that although 223 participants opted out of getting a bivalent booster due to the belief they were already protected against infection and/or severe disease, 71.7% (n = 160) had not had a COVID-19 infection or vaccination within the last 6 months, and 51.1% (n = 114) had never been infected.
After reading the information about the COVID-19 bivalent booster vaccine, 67.8% said they now planned to receive it. Among those who specifically reported being unaware of their eligibility, 88.0% said they would get the bivalent booster.
After 1 month, the 714 participants who had not initially received a bivalent booster were sent a second survey; 87.4% (n = 624) completed the follow-up survey. Of the 68.4% (n = 427) participants who previously indicated plans to receive the bivalent booster, 28.6% (n = 122) had done so. Among the 197 respondents who had not planned to get the bivalent booster, 4.6% (n = 9) had received it after all. Of the 305 participants who planned to get the bivalent booster but had yet to do so, 82.6% (n = 252) still planned to get it, 1.0% (n = 3) no longer planned to get it, and 16.4% (n = 50) were unsure.
The most common reasons recontacted participants gave for not getting the bivalent booster were being too busy (35.6%), forgetting (22.7%), and worrying about side effects (22.7%).
The study authors noted that only 12.1% of all adults had received a bivalent booster shot at the time the survey was conducted, and today this has only increased to 18.2% of eligible adults. Overall, they wrote, the survey responses reveal health care providers and other “trusted messengers” should increase awareness of bivalent booster eligibility criteria, availability, and safety and efficacy.
“Increasing bivalent booster vaccination coverage will require a multifaceted approach to address reasons for nonvaccination,” the CDC concluded, emphasizing, “All eligible adults should receive a bivalent booster dose to protect themselves against SARS-CoV-2 infection and severe disease.”