Efficacy

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

FA Manian MD, MPH, , , , , , , , Leave a comment

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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References

  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. https://www.cdc.gov/mmwr/volumes/70/wr/mm7018e1.htm?s_cid=mm7018e1_w
  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. https://www.nejm.org/doi/10.1056/NEJMoa2101765
  3. Mueller AL, McNamara MS, Sinclair DA. Why does COVID-19 disproportionately affect older people. Aging (Albany NY) 2020;12:9959-9981. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7288963/

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?

How effective are the current Covid-19 vaccines in reducing the risk of asymptomatic infection?

FA Manian MD, MPH, , , , , , Leave a comment

Limited data suggest that not only are the mRNA Covid-19 vaccines effective in reducing the risk of symptomatic disease  by greater than 90% but also reducing the risk of asymptomatic infections by 80-90% after the second dose and by 62-80% after the 1st dose. 1-3

A CDC study of health care personnel, first responders, and other essential and frontline workers who received one of the 2 currently available mRNA vaccines (BNT162b2-Pfizer or mRNA-1273-Moderna) and underwent weekly testing for SARS-CoV-2 infection irrespective of symptoms found 90% efficacy in preventing infection among fully immunized (≥14 days after 2nd dose) and 80% efficacy in preventing infection among the partially immunized (≥14 days after 1st dose).  The majority of SARS-CoV-2 infections were identified by weekly specimens, with 11% remaining without symptoms.1

In a retrospective study of over 39,000 asymptomatic adult patients undergoing pre-procedural SARS-CoV-2 molecular screening tests, an 80% reduction in the risk of a positive test  was observed in those who had received 2 doses of an mRNA vaccine (majority Pfizer) and 72% reduction in those following a single dose of vaccine >10 days prior to their pre-procedure test.2  In the original Moderna trial , a 62% reduction in the risk of asymptomatic infection was seen among participants just before the second dose (ie, partially immunized).3 

Collectively, these reports support the high efficacy of mRNA vaccines in reducing the risk of SARS-CoV-2 in asymptomatic infection.  Whether these findings can be reproduced with other vaccine preparations is not known at this time!

Bonus Pearl: Did you know that according to 1 study, asymptomatic patients with SARS-CoV-2 infection may be more likely to be women, younger and have shorter duration of viral shedding? 4

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References

  1. Thompson MG, Burgess JL, Naleway AL, et al. Interim estimates of vaccine effectiveness of BNT162b2 and mRNA-1273 Covid-19 vaccines in preventing SARS-CoV-2 infection among health care personnel, first responders, and other essential and frontline workers—Eight U.S. locations, December 2020-March 2021. https://www.cdc.gov/mmwr/volumes/70/wr/mm7013e3.htm
  2. Tande AJ, Pollock BD, Shah ND, et al. Impact of the Covid-19 vaccine on asymptomatic infection among patients undergoing pre-procedural Covid-19 molecular screening. Clin Infect Dis 2021. https://pubmed.ncbi.nlm.nih.gov/33704435/
  3. Baden LR, El Sahly HM, Essink B, et al. Efficacy and safety of the mRNA-1273 SARS-CoV-2 vaccine. N Engl J Med 2021;384:403-16. https://www.nejm.org/doi/full/10.1056/nejmoa2035389
  4. Yang R, Gui X, Xiong Y. Comparison of clinical characteristics of patients with asymptomatic vs symptomatic coronavirus disease 2019 in Wuhan, China. JAMA Network Open 2020; May 27. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2766237

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 current Covid-19 vaccines in reducing the risk of asymptomatic infection?