Study assesses COVID-19 booster vaccination coverage by demographics and behaviors and experiences toward vaccination among fully vaccinated adults

By Dr. Liji Thomas, MDReviewed by Danielle Ellis, B.Sc.Dec 15 2022

An early release from the Centers for Disease Control and Prevention (CDC), USA, examines the coverage of booster doses among adults in the USA.

Introduction

Booster doses of a vaccine are designed to enhance the immune response to provide more durable and effective protection once that induced by the primary protocol has waned. The recommendation to give booster doses of the coronavirus disease 2019 (COVID-19) vaccine came after some studies showed improved immunity by adding a booster dose to the protocol.

Not only did the antibody titer go up following the booster dose, but the breadth of protection increased, including both Delta and Omicron variants of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This was claimed to reduce hospitalization rates and disease severity following infection.

For instance, messenger ribonucleic acid (mRNA) vaccines produced up to 86% fewer emergency department (ED) visits due to COVID-19 during the Delta waves after the second dose of the vaccine according to the primary protocol – but this rose to 94% with a booster dose. With Omicron, the comparable figures were up to 52% and 82%, respectively. Hospitalizations also went down still further following the administration of a booster dose.

Booster doses were recommended for all eligible adults on November 29, 2021. The objective was to reduce the severity and death rates, as well as COVID-19 spread in the country.

The current study, published in Emerging Infectious Diseases,  looked at adult booster dose coverage between February 27 and March 26, 2022, when almost 85% of Americans received the primary series of COVID-19 vaccines. The results come from an analysis of the data collected for the National Immunization Survey–Adult COVID Module.

What did the study show?

The scientists found that almost two out of three fully vaccinated adults had taken one or more booster doses at this time point. This was a significant increase from the earlier level of just over a quarter in November 2021. Most of the increase came from older adults (over 50 years of age), with under-65s and over-65s showing coverage rates of 66% and 80%, respectively.

Again, a higher household income was associated with greater booster coverage, as was a higher education level and insurance.

When stratified by race or ethnicity, Asian and White adults were the most likely to have received booster doses, at approximately 75% and 68%, respectively. In comparison, only about 53% and 56% of Blacks and Hispanics/American Indians or Native Alaskans fell into this category. Natives of Hawaii or the Pacific Islands still had lower coverage, at 45%.

When occupations were compared, essential healthcare workers and childcare or school workers had received booster doses in two of three cases, higher than other essential workers.

Among adults with other conditions, 70% of those with other diseases and 62% with a disability had received booster doses. At all ages, disability was linked to lower coverage. Again, lower booster coverage was linked to little difficulty obtaining the vaccine.

Only a tenth or less of fully vaccinated adults who failed to get a booster dose cited such difficulties as the reason.

Socially vulnerable localities had a lower coverage rate, as did those with a history of COVID-19. People who feared getting COVID-19 were more likely to get the booster than others. Increased coverage was seen among those who felt the vaccines were safe and effective, as well as when almost all family members and friends had been vaccinated.

About 40% of those who did not take a booster dose after a primary series expressed some concern about vaccine safety, and a fifth doubted their utility against COVID-19. Approximately two-thirds of them, especially younger adults, did not fear getting the disease.

What are the implications?

Overall, about 53% of adults in the USA have been fully vaccinated and received one or more booster doses. The report indicates suboptimal booster dose coverage across the USA.

Racial and ethnic factors seem to be operating with respect to acceptance and/or access to booster doses, along with other contributing factors. Other adverse factors include low social status, lower education, and lower income, besides the presence of disability and a prior COVID-19 history. Those who feared getting the disease were more likely to get the booster, as were those who believed in its safety and effectiveness.

“Tailored strategies are needed to educate the public and reduce disparities in COVID-19 vaccination coverage.” Access and attitudinal barriers need to be overcome to achieve better uptake.

Healthcare providers (HCPs) should play a role in recommending booster doses to their eligible adult patients. over half of those who did not receive a booster indicated that they had not been recommended to get any COVID-19 vaccine by an HCP.

When family and friends were vaccinated, booster dose uptake was increased, indicating the vital role of social example and the potential usefulness of community healthcare workers in promoting booster uptake. Other interventions could include vaccination incentives and onsite vaccination, along with reminders to get a booster dose.