COVID Vaccine Uptake - Credit CDC
#17,472
Between vaccine fatigue, the emergence of a less virulent Omicron variant, and the constant anti-vaccine rhetoric on social media, the uptake of the new bivalent COVID vaccine introduced last fall has been disappointing.
Only about 17% of Americans have embraced the shot, although among those 65 or older, that number jumps to 42%.
Admittedly, the shot struggles to prevent infections, particularly since the emergence late last year of XBB (recombinant) variants, however evidence continues to suggest it can still reduce the risks for severe illness, hospitalization, and death.
About a month ago, the CDC endorsed the FDA's recommendation to authorize a second bivalent booster shot for specific groups (primarily those > 65 and immunocompromised patients), and a streamlining of the booster process for practically everyone else (see COCA Call: Updated Recommendations for COVID-19 Vaccine Use).
While there are plans to roll out an XBB-specific vaccine in the fall (see WHO Recommends Switching To A Monovalent XBB based COVID Vaccine), until then the bivalent vaccine is our best pharmacological defense against the virus.
This week, the CDC's MMWR carries a detailed report on the durability of the vaccine's protection over the first 6 months.
While its ability (in non-immunocompromised individuals) to prevent hospitalizations waned from 62% to 24% after 4 months, it was more effective in preventing deaths. This suggests that those who received a bivalent booster last fall are at or near the end of its protection.
The link, summary, and some excerpts from the report follow. I'll have a brief postscript after the break.
Estimates of Bivalent mRNA Vaccine Durability in Preventing COVID-19–Associated Hospitalization and Critical Illness Among Adults with and Without Immunocompromising Conditions — VISION Network, September 2022–April 2023
Weekly / May 26, 2023 / 72(21);579–588Ruth Link-Gelles, PhD1; Zachary A. Weber, PhD2; Sarah E. Reese, PhD2; Amanda B. Payne, PhD1; Manjusha Gaglani, MBBS3,4; Katherine Adams, MPH5; Anupam B. Kharbanda, MD6; Karthik Natarajan, PhD7,8; Malini B. DeSilva, MD9; Kristin Dascomb, MD, PhD10; Stephanie A. Irving, MHS11; Nicola P. Klein, MD, PhD12; Shaun J. Grannis, MD13,14; Toan C. Ong, PhD15; Peter J. Embi, MD16; Margaret M. Dunne, MSc2; Monica Dickerson5; Charlene McEvoy, MD9; Julie Arndorfer, MPH10; Allison L. Naleway, PhD11; Kristin Goddard, MPH12; Brian E. Dixon, PhD13,17; Eric P. Griggs, MPH1; John Hansen, MPH12; Nimish Valvi, DrPH13; Morgan Najdowski, MPH1; Julius Timbol, MS12; Colin Rogerson, MD13; Bruce Fireman12; William F. Fadel, PhD13,17; Palak Patel, MBBS5; Caitlin S. Ray, MPH5; Ryan Wiegand, PhD1; Sarah Ball, ScD2; Mark W. Tenforde, MD, PhD5
Summary
What is already known about this topic?
Bivalent mRNA COVID-19 vaccines help provide protection against medically attended COVID-19–associated illness. However, the durability of this protection is uncertain.
What is added by this report?
Among adults aged ≥18 years without immunocompromising conditions, bivalent booster vaccine effectiveness (VE) against COVID-19–associated hospitalization declined from 62% at 7–59 days postvaccination to 24% at 120–179 days compared with VE among unvaccinated adults. Among immunocompromised adults, lower bivalent booster VE was observed. However, bivalent booster VE was sustained against critical COVID-19–associated outcomes, including intensive care unit admission or death.
What are the implications for public health practice?
Adults should stay up to date with recommended COVID-19 vaccines. Optional additional bivalent vaccine doses are available for older adults and persons with immunocompromising conditions.
(SNIP)
As of May 10, 2023, only one in five (20.5%) U.S. adults had received a bivalent booster dose.*** Among U.S. adults who previously received a monovalent vaccine but had yet to receive a bivalent mRNA booster, most received their last vaccine dose >1 year ago.††† Results of this analysis indicate that these adults might have relatively little remaining protection against COVID-19–associated hospitalization compared with unvaccinated persons, although might have more remaining protection against critical illness.
On April 19, 2023, CDC amended recommendations to permit adults aged ≥65 years and those with immunocompromising conditions to receive ≥1 additional bivalent dose. In this analysis, waning VE patterns were the same in younger and older adults; however, rates of COVID-19–associated hospitalization and death remain substantially higher among older adults, which suggests that an additional dose might confer additional benefit. In addition, although this analysis did not demonstrate clear evidence of waning VE in immunocompromised adults, overall VE among immunocompromised adults was lower than among those without immunocompromising conditions. Like older adults, persons with immunocompromising conditions remain at higher risk for COVID-19 hospitalization and death and might benefit from additional bivalent doses, although this will require future evaluation.
The findings in this study are subject to at least six limitations.
- First, previous SARS-CoV-2 infection was not accounted for in this analysis. According to a national seroprevalence survey, a large proportion of the population has now experienced SARS-CoV-2 infection; infection-induced immunity decreases the risk for future medically attended COVID-19 illness and might affect observed VE.§§§ The findings of this analysis should therefore be interpreted in the context of this underlying immunity as the incremental benefit provided by COVID-19 vaccination.
- Second, although all case-patients included in the analysis had COVID-19–like illness and a positive SARS-CoV-2 test result at the time of the included hospitalization, some might have had relatively mild COVID-19 disease and been hospitalized because of reasons unrelated to COVID-19, which could lower measured VE.
- Third, although models adjusted for relevant confounders, such as age and calendar time, residual confounding is possible, including by behavioral differences, history of previous SARS-CoV-2 infection, and use of COVID-19 treatments such as nirmatrelvir-ritonavir (Paxlovid).
- Fourth, differences in sublineage-specific VE could not be compared because of limited statistical power.
- Fifth, this analysis did not compare product-specific bivalent booster VE estimates.
- Finally, because these data are from seven states, the patients in this analysis might not be representative of the entire U.S. population.
In this study of durability of bivalent VE, bivalent doses helped provide protection against COVID-19–associated hospitalization and critical disease. Although waning of protection was evident in some groups, VE was more sustained for critical illness, indicating the vaccines are continuing to help protect adults from the most severe COVID-19 outcomes. All adults should stay up to date with recommended COVID-19 vaccines.
While North America and much of Europe appear to be enjoying a relative lull in COVID activity the same cannot be said for China, parts of Asia, Africa, and the Western Pacific (see WHO COVID Weekly Epidemiological Report).
