The vexed question of flu shots and the risk of Covid-19
Will Covid-19 finally vanquish the anti-vaccination movement? To answer the question Katrina Megget elicits comments from five experts in public health and vaccine politics. (BMJ 2020;369:m2184, June 4) They reach no firm conclusion, but Barry Bloom calls for a vast advocacy campaign and mass screening of social media with harmful misinformation removed. He does not specify what qualifies as “harmful misinformation.”
It has recently come to light that the countries with the highest Covid-19 death rates also have the highest rates of influenza vaccine uptake among the elderly. (www.bmj.com/content/369/bmj.m1932/rr-15) For 20 European countries there was a strong geographic correlation: r=0.730, P<<0.001. I recently updated this and the correlation persists: r=0.744, P<<0.001. (www.worldometers.info/coronavirus, 6/6/20)
“Correlations can be treacherous.” So said The Lancet more than 40 years ago. (Editorial, “The Anomaly That Wouldn’t Go Away” November 4, 1978, page 978) Would Dr. Bloom consider the foregoing correlation to be treacherous? Would he say it is “harmful misinformation”?
This correlation is consistent with case-control studies and one randomized trial associating flu shots with non-influenza virus infections/NIRVs, including coronaviruses. (Cowling et al, Clin Infect Dis 2012;54:1778. Kelly et al, Pediatr Inf Dis J 2011;30:107. Wolff, Vaccine 2020;38:350) There are plausible immune mechanisms, including virus interference, indicating that this could be a causal association.
Danuta Skowronski and her Canadian colleagues recently found that influenza vaccine had “no effect on coronavirus or other NIRV risk.” Furthermore, they re-analyzed Wolff’s study and identified a methodological problem to account for the unexpected 36% increase in risk of coronavirus infection that he found associated with influenza vaccine. (Skowronski et al, Clin Infect Dis, 5/22/20. https://doi.org(10.1093/cid/ciaa626) However, their Table 1 indicates statistically non-significant trends associating influenza vaccination with NIRVs in general and with coronavirus in particular. Crucially, they provide no specific data for the 65+ age group.
Would Dr. Bloom or anyone else in authority consider pursuing the foregoing influenza vaccine/coronavirus/Covid-19 associations?
It remains to be seen whether we ever have a safe and effective vaccine for Covid-19. A number of eminent authorities have expressed serious doubts, and they are not part of “the anti-vaccination movement.” Meanwhile, randomized trials of BCG vaccination are now underway to see if it could reduce the impact of Covid-19. (Curtis et al, Lancet 2020;395:1545, May 16) They were motivated in part by moderate geographic correlations between BCG use and Covid-19 death rates: countries with a long history of BCG use now have substantially lower Covid-19 death rates than countries with shorter histories or non-use of BCG. (Miller et al, medRxiv. https://doi.org/10.1101/2020.03.24.20042937)
A number of factors are believed to affect the large geographic variation in the frequency of Covid-19 disease. One of these is population density, but it is interesting that the geographic correlation of country population density (Wikipedia, 6/6/20) with Covid-19 death rates (www.worldometers.info.coronavirus, 6/6/20) is weak: r=0.380, P=0.1.
One more sour note about influenza vaccination. An observational study with a regression discontinuity design looked at mortality in the elderly over a 14-year period. (Anderson et al, Ann Intern Med 2020;172:445. doi:10.7326/M19-3075. Epub 2020 Mar 3) Table 2 indicates that influenza vaccine was associated with an 8.9% increase in All Cause Mortality in elderly men (VE –8.9%, CI –19.6% to 1.8%), and a 26.5% increase in Pneumonia and Influenza Mortality (VE –26.5%, CI –56.1% to 3%).
Scott Ratzan is quoted at the end of Katrina Meggett’s article: “The pandemic is showing our vulnerabilities when it comes to vaccines and vaccine hesitancy—and it raises the matter of how we protect for future pandemics. This isn’t just a rights matter. This is a community protection matter. Vaccines are our only hope.” Really? In light of the foregoing, some students of the subject might consider this statement an example of “harmful misinformation.”
ALLAN S. CUNNINGHAM 8 June 2020
Competing interests: No competing interests