What’s the connection between flu vaccination and lower risk of Alzheimer’s Disease?

As far fetched that it may sound, there is growing evidence that flu vaccination is associated with lower risk of being diagnosed with Alzheimer’s Disease (AD).1

The most compelling evidence to date comes from a 2022 retrospective, propensity-matched study involving a nationwide sample of over 2 million U.S. adults ≥ 65 years old.1  This study found a 40% reduction in the risk of incident AD during the 4-year follow-up period when individuals receiving at least 1 dose of flu vaccine were compared to those who did not receive flu vaccination during the study period (number needed to treat-NTT 29.4). 

Despite its limitations, the results of the above study were concordant with those of several smaller studies that found an association between flu vaccination and lower risk of dementia of any cause.1-3  A 2022 meta-analysis also concluded that flu vaccination was associated with significantly lower risk (33%) of dementia among older people. Interestingly, in a study involving veterans, receipt of ≥6 doses of flu vaccines (not fewer) was associated with lower risk of dementia.4

Several hypotheses have been posited to explain the potential beneficial impact of flu vaccination on the risk of dementia, including: 1. Influenza-specific mechanisms, such as mitigation of damage secondary to influenza infection and/or epitopic similarity between influenza proteins and AD pathology; 2. Non-influenza-specific training of the innate immune system; and 3. Non-influenza-specific changes in adaptive immunity via lymphocyte-mediated cross-reactivity.1

So, in addition to its protective effect against severe influenza,5 and its association with lower risk of hospitalization for cardiac disease and stroke and reduction in death due to combined cardiovascular disease events (eg, heart attacks/strokes),  flu vaccination may be protective against AD! Who would have thought that a simple vaccine may have far reaching health benefits?

Bonus Pearl: Did you know that mice infected with non-neurotropic influenza strains have been found to have excessive microglial activation and subsequent alteration of neuronal morphology, particularly in the hippocampus, and that in APP/PS1 transgenic mice, peripheral influenza infection induces persistent elevations of amyloid- (A) plaque burden?Intriguing indeed!!!

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References

  1. Bukhbinder AS, Ling Y, Hasan O, et al. Risk of Alzheimer’s disease following influenza vaccination: A claims-based cohort study using propensity score matching. Journal of Alzheimer’s Disease 2022; 88:1061-1074. https://pubmed.ncbi.nlm.nih.gov/26945371/  
  2. Liu JC, Hsu YP, Kao PF, et al. Influenza vaccination reduces dementia risk in chronic kidney disease patients: A population-based cohort study. Medicine (Baltimore) 2016 95 :32868. https://pubmed.ncbi.nlm.nih.gov/26945371/
  3. Wiemken TL, Salas J, Hoft DF, et al. Dementia risk following influenza vaccination in a large veteran cohort. Vaccine 2021;39:5524-5531. https://pubmed.ncbi.nlm.nih.gov/34420785/
  4. Veronese N, Demurtas J, Smith L, et al. Influenza vaccination reduces dementia risk: A systematic review and meta-analysis. Ageing Res Rev 2022;73:101534. https://pubmed.ncbi.nlm.nih.gov/34861456/
  5. Godoy P, Romero A, Soldevila N, et al. Influenza vaccine effectiveness in reducing severe outcomes over six influenza seasons, a case-cae analysis, Spain, 2010/11 to 2015/16.  Euro Surveill 2018;23:1700732. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6208006/
  6. Hosseini S, Michaelsen-Preusse K, Schughart K, et al. Long-term consequences of non-neurotropic H3N2 influenza A virus infection for the progression of Alzheimer’s Disease symptoms. Front. Cell. Neurosci 28 April 2021; https://doi.org/10.3389/fncel.2021.643650 https://www.frontiersin.org/articles/10.3389/fncel.2021.643650/full

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, Massachusetts General Hospital, Harvard Catalyst, Harvard University, their affiliate academic healthcare centers, or its contributors. 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!

 

What’s the connection between flu vaccination and lower risk of Alzheimer’s Disease?

My middle-age immunocompromised patient receiving immunosuppressants has had 3 doses of mRNA Covid vaccine and is now 4 months out from her 3rd dose.  Should she consider a fourth dose of Covid vaccine?

Yes! According to the Centers for Disease Control and Prevention (CDC) of the U.S.,1 persons who are “moderately or severely immunocompromised” and have received 3 doses of an mRNA vaccine (either Pfizer [12+ years old) or Moderna (18+ years old]) should receive a 4th dose (“booster”) at least 3 months after the 3rd dose.  Similarly, those who initially received a J&J vaccine followed by one of the aforementioned mRNA vaccines and are at least 2 months from the 2nd dose should also receive a 3rd dose (booster. 

The following are considered moderately or severely immunocompromised conditions by CDC: 

  • Active cancer treatment for tumors or cancers of the blood
  • Organ transplant with immunosuppressants on board
  • Stem cell transplant within the last 2 years or taking immunosuppressants
  • Moderate or severe primary immunodeficiency (eg, DiGeorge or Wiskott-Aldrich syndromes)
  • Advanced or untreated HIV infection
  • Active treatment with high-dose corticosteroids or other immunosuppressants

A published study2 of Covid-19-associated emergency department (ED) and urgent care (UC) encounters and hospitalization among adults during a period including Omicron variant predominance in 10 states found vaccine effectiveness for ED/UC visits dropping to 66% and for hospitalization to 78% by the 4th month after a 3rd dose (vs 87% and 91%, respectively during the 2 months after a 3rd dose).  This study did not distinguish immunocompromised from non-immunocompromised persons, however.  More data on the vaccine effectiveness in non-immunocompromised persons at high risk of Covid-19 related complications would be welcome.

Bonus Pearl: Did you know that of American adults who are fully vaccinated against Covid-19, only about 30% have received an additional Covid vaccine dose beyond the primary series3 

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References

  1. Covid-19 vaccines for moderately or severely immunocompromised people (Updated Feb 17, 2022). Accessed Feb 21, 2022.  https://www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/immuno.html?s_cid=10483:immunocompromised%20and%20covid%20vaccine:sem.ga:p:RG:GM:gen:PTN:FY21
  2. Waning 2-doe and 3-dose effectiveness of mRNA vaccines against Covid-10-associated emergency department and urgent care encounters and hospitalizations among adults during periods of delta and omicron variant predominance—Vision Network, 10 states, August 2021-January 2022. MMWR 2022; 71:255-63. https://www.cdc.gov/mmwr/volumes/71/wr/mm7107e2.htm?s_cid=mm7107e2_w
  3. Hubler S, Harman A. As Cov id surges, experts say U.S. booster effort is falling behind. NY Times, December 18, 2021. https://www.nytimes.com/2021/12/18/us/omicron-booster-shots-americans.html

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, Massachusetts General Hospital, Harvard Catalyst, Harvard University, their affiliate academic healthcare centers, or its contributors. 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!

My middle-age immunocompromised patient receiving immunosuppressants has had 3 doses of mRNA Covid vaccine and is now 4 months out from her 3rd dose.  Should she consider a fourth dose of Covid vaccine?

What’s the evidence that a third dose of mRNA Covid-19 vaccine reduces risk of Covid-19 disease?

The strongest evidence to date demonstrating the effectiveness of a third dose of mRNA Covid-19 vaccine comes from an observational study from Israel which reported 93% effectiveness for admission to hospital, 92% for severe disease and 81% for Covid-19 related deaths when compared to those who had received 2 doses of the vaccine (Pfizer, BNT162b2 mRNA) at least 5 months before.1

This was a large population-based study involving over a million people 16 years or older (one-half in each group) who were eligible for the third dose (median age 52 y); those living in long-term facilities, healthcare workers and those medically confined to their homes were excluded. Vaccine effectiveness was evaluated at least 7 days after receipt of the third dose.  Median follow-up period was 13 days for both groups.

Overall effectiveness of the third dose vs 2 vaccine doses was 93% (88-97) for admission to hospital, 92% (82-97) for severe disease and 81% for death (59-97). Effectiveness of the third dose was similar between males and females and between individuals 40-60 years and those at least 70 years of age; effectiveness could not be determined in the younger age group due to small number of adverse outcomes.

What makes this study stand out among the previous works2,3 is that it controlled for important possible confounders, including sociodemographic factors, clinical factors, and behavioral factors related to Covid-19.  Limitations include its observational nature and exclusion of certain at risk groups, such as nursing home residents and healthcare workers.

Given the increasing number of Covid-19 cases in many communities at this writing, the news that a booster shot of an mRNA vaccine provides further protection in preventing Covid-19 is very welcome!

Bonus Pearl: Did you know that in a study measuring the immune response after the third dose of an mRNA vaccine (Moderna) in those 60 years of age or older, the median antibody titer rose 50-fold!4

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References

  1. Barda N, Dagan N, Cohen C, et al. Effectiveness of a third dose of the BNT162b2 mRNA Covid-19 vaccine for preventing severe outcomes in Israel: an observational study. Lancet, published online October 29, 2021. https://www.thelancet.com/action/showPdf?pii=S0140-6736%2821%2902249-2
  2. Bar-On YM, Goldberg Y, Mandel M, et al. Protection of BNT162b2 vaccine.N Engl J Med 2021; published online Sept 15, https://doi.org/10.1056/nejmoa21114255.
  3. Patalon T, Gazit S, Pitzer VE, et al. Short term reduction in the odds of testing positive for SARS-CoV-2; a comparison between two doses and three doses of the BNT162b2 vaccine. medRxive 2021;published online Aug 31. https://doi.org/10.1101/2021.008.29.21262792 (preprint).
  4.  Eliakim-Raz N, Liebovici-Weisman Y, Stemmer A, et al. Antibody titers before and aftera third dose of SARS-CoV-2 BNT162b2 vaccine in adults ages ≥60 years. JAMA. Published online November 5, 2021. doi:10.1001/jama.2021.19885 https://jamanetwork.com/journals/jama/fullarticle/2786096

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, Massachusetts General Hospital, Harvard Catalyst, Harvard University, their affiliate academic healthcare centers, or its contributors. 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!

What’s the evidence that a third dose of mRNA Covid-19 vaccine reduces risk of Covid-19 disease?

What’s the evidence that immunocompromised patients need a 3rd booster mRNA Covid vaccine shot?

At this time, the Centers for Disease Control and Prevention (CDC) recommendation for a booster shot of an mRNA vaccine in patients with moderate to severe immunocompromised state (1,2) is based primarily on the concern for waning immunity following the initial series—including a decline in neutralizing antibodies— in this patient population, and the finding that at least some immunocompromised patients may have a significant improvement in certain laboratory measurements of immunity following their booster shot. 

Although there are no randomized-controlled trials of the efficacy of the 3rd shot in protecting against Covid-19 in immunocompromised patients, the recent surge in the highly transmissible SARS-CoV-2 variants in many parts of the world (including the U.S.)  as well as immunocompromised patient population accounting for nearly one-half of all breakthrough Covid-19 cases requiring hospitalization (1) make it urgent to adopt these recommendations. 

A randomized trial involving 120 solid organ transplant patients (median age 67 y) found higher neutralizing antibody levels and SARS CoV-2 specific T-cell counts after the mRNA-1273 (Moderna) vaccine booster dose compared to placebo (3).

In another study involving 101 solid organ transplant patients, of 59 subjects who were seronegative before the 3rd dose, 44% became seropositive 4 weeks after the 3rd vaccine dose ( BNT162b2-Pfizer vaccine administered 2 months after the second dose). Patients who did not have an antibody response were older, had higher degree of immunosuppression and had a lower estimated glomerular filtration rate than those with antibody response (4).

A “spectacular increase” in anti-spike antibodies with levels close to the general population has also been reported among hemodialysis patients receiving a third dose of Pfizer mRNA vaccine (5). 

Until further data from larger studies become available,  these studies support administration of a 3rd dose booster mRNA vaccine in moderate to severely immunosuppressed individuals.

Bonus Pearl: Did you know that although immunocompromised patients have significantly worse influenza outcome, the data on the impact of immunocompromised status on the outcome of Covid-19 is less clear with published evidence that both supports and refutes this association (6)?  

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References

  1. CDC. Data and clinical considerations for additional doses in immunocompromised people: ACIP Meeting, July 22, 2021. ACIP Data and Clinical Considerations for Additional Doses in Immunocompromised People (cdc.gov)
  2. CDC. Interim clinical considerations for use of Covid-19 vaccines currently authorized in the United States. August 13, 2021. Interim Clinical Considerations for Use of COVID-19 Vaccines | CDC
  3. Hall VG, Ferreira VH, Ku T, et al. Randomized trial of a third dose of mRNA-1273 vaccine recipients. N Engl J Med 2021, Aug 11. Randomized Trial of a Third Dose of mRNA-1273 Vaccine in Transplant Recipients | NEJM
  4. Kamar N, Abravanel F, Marion O. Three doses of an mRNA Covid-19 vaccine in solid-organ transplant recipient. N Engl J Med 2021, Aug 12.Three Doses of an mRNA Covid-19 Vaccine in Solid-Organ Transplant Recipients | NEJM
  5. Frantzen L, Thibeaut S, Moussi-Frances J, et al. Covid-19 vaccination in haemodialysis patients: Good things come in threes… Neph Dial Transplant, 20 July 2023. COVID-19 Vaccination in Haemodialysis Patients: Good things come in threes… – PubMed (nih.gov)
  6. Parisi C. An opportunity to better understand the impact of coronavirus on immunocompromised patients. J Infect Dis 2021;224:372-3. Opportunity to Better Understand the Impact of Coronaviruses on Immunocompromised Patients | The Journal of Infectious Diseases | Oxford Academic (oup.com)

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy-St. Louis, Massachusetts General Hospital, Harvard Catalyst, Harvard University, their affiliate healthcare centers, or its contributors. 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!

What’s the evidence that immunocompromised patients need a 3rd booster mRNA Covid vaccine shot?

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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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?

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?