How effective are the mRNA Covid-19 vaccines in reducing the risk of hospitalization among adults 65 years of age or older?

The mRNA vaccines by Pfizer and Moderna seem very effective in not only reducing risk of symptomatic Covid-19 but also risk of hospitalization among adults 65 years of age or older.   A CDC study published on April 28, 2021, showed a vaccine efficacy of 94% among fully immunized and 64% among partially immunized adults ≥ 65 years of age  with approximately one-half of subjects  ≥75 years old.1

This study was carried out in 24 hospitals in 14 states in the U.S. during January 1, 2021-March 26, 2021, and involved 417 patients: 187 case-patients with Covid-19 and 230 controls with negative SARS-CoV-2 PCR test.  Among patients with Covid-19, 10% were partially immunized (vs 27% among controls) and 0.5% were fully immunized (vs. 8% among controls). 1

An Israeli study in a nationwide mass vaccination setting involving persons (28% ≥ 60 y) receiving Pfizer mRNA vaccine similarly found a vaccine efficacy of 74% for hospitalization for partially immunized and 87% for fully immunized persons.2

The high effectiveness of mRNA vaccines against more severe Covid-19 requiring hospitalization is great news, of course, as advanced age is by far the greatest risk factor for death from Covid-19, independent of underlying comorbidities.3   

Bonus Pearl: Did you know that prior to the availability of effective Covid-19 vaccination, adults over 65 years of age represented 80% of hospitalizations and had a 23-fold greater risk of death than those under 65?3

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  1. Tenforde MW, Olson SM, Self WH, et al. Effectiveness of Pfizer-BioNTech and Moderna vaccines against COVID-19 among hospitalized adults aged ≥65 years-United States, January-March 2021.
  2. Dagan N, Barda N, Kepten E, et al. BNT162b2mRNA Covid-19 vaccine in a nationwide mass vaccination setting. N Engl J Med 2021;384:1412-1423.
  3. Mueller AL, McNamara MS, Sinclair DA. Why does COVID-19 disproportionately affect older people. Aging (Albany NY) 2020;12:9959-9981.

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis or its affiliate healthcare centers, Mass General Hospital, Harvard Medical School or its affiliated institutions. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

How effective are the mRNA Covid-19 vaccines in reducing the risk of hospitalization among adults 65 years of age or older?

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