Flu shots and the risk of coronavirus infections
John Watkins is right; we need to think beyond containment, but he overlooks the possibility that seasonal flu shots are potential contributors to the current outbreak. (BMJ 2020;398:m810—February 28)….A randomized placebo-controlled trial in children showed that flu shots increased fivefold the risk of acute respiratory infections caused by a group of noninfluenza viruses, including coronaviruses. (Cowling et al, Clin Infect Dis 2012;54:1778) From Table 3, vaccine recipients had 20 noninfluenza virus-positive ARIs and 19 virus-negative ARIs; non-recipients had 3 noninfluenza virus-positive ARIs and 14 virus-negative ARIs. These figures yield an odds ratio of 4.91 (CI 1.04 to8.14).
Such an observation may seem counterintuitive, but it is possible that influenza vaccines alter our immune systems non-specifically to increase susceptibility to other infections; this has been observed with DTP and other vaccines. (Benn et al, Trends in Immunology, May 2013) There are other immune mechanisms that might also explain the observation.
To investigate this possibility, a case-control study is in order as we study and care for the victims of covid-19. Influenza vaccines have become sacred cows in some quarters, but they shouldn’t be.
ALLAN S. CUNNINGHAM 2 March 2020
Competing interests: No competing interests