Is the Flu Vaccination Associated with Increased Risk of Other Respiratory Viruses?

by | Jun 4, 2020 | 2020, Lung Health, Respiratory Health, Vaccines

Written by Angeline A. De Leon, Staff Writer. Study data revealed that when comparing vaccinated vs. unvaccinated individuals, those receiving influenza vaccination had an increased risk of infection with coronavirus and human metapneumovirus.

The Spanish Flu Pandemic of 1918, estimated to be responsible for approximately 50 million deaths worldwide, spurred the creation of the first influenza vaccination in the U.S. during the late 1930s 1. Since that time, flu vaccines have been shown to significantly reduce the seasonal circulation of the virus 2,3. While previous research has suggested that natural infection by the flu virus can actually protect against other respiratory viruses by temporarily bolstering general immunity against non-influenza viruses 4,5, more recent studies suggest the opposite effect. Vaccine-associated virus interference refers to the increased risk of other respiratory viruses as a result of receiving flu vaccination, the hypothesis being that vaccinated individuals who do not receive the general immunity associated with natural infection will become more likely to contract other respiratory viruses 6,7. The literature has remained somewhat mixed, with some research suggesting that the flu vaccine may not be associated with virus interference at all 8. In a 2020 study 9 published in Vaccine, an investigation was undertaken to evaluate virus interference in Active Duty and Reserve Component personnel of the Department of Defense (DoD), a population for whom influenza vaccination is mandatory 10.

During the 2017-2018 influenza season, a total of 9,469 DoD personnel (aged 18-35 years) submitted a respiratory specimen for laboratory testing. Influenza virus and other respiratory pathogen panels, including adenovirus, coronavirus, human metapneumovirus, and other co-infections, were evaluated. Vaccination status was obtained using surveys completed by participants at the time of respiratory sample collection and from immunization tracking data sourced from a United States Air Force database. Individuals with a non-influenza respiratory virus were compared to those with pan-negative results (no pathogen detected). Influenza positive cases were then compared to three different control groups: an all-control group (those testing negative for flu or positive for any other non-influenza respiratory virus), a non-influenza positive control group (those testing positive for any non-influenza respiratory virus), and a pan-negative control group. Finally, adjusted and unadjusted odds ratios (OR) were calculated.

Across all participants, tests identified a total of 3,349 influenza positive cases, a total of 2,880 non-influenza positive respiratory virus cases, and a total of 3,240 pan-negative cases. Among the 6,541 individuals who received a flu vaccination, 31.3% contracted the flu, 31.3% contracted a non-influenza respiratory virus, and 37.4% tested negative for any pathogen. Comparing vaccinated participants to those unvaccinated, adjusted OR for non-influenza respiratory viruses was calculated as 0.97 (95% Confidence Interval: 0.86 to 1.09) (p = 0.60). Adjusted ORs for influenza cases vs. all-controls, non-influenza virus positive controls, and pan-negative controls, respectively, were 0.48 (95% CI: 0.43 to 0.52), 0.51 (95% CI: 0.45 to 0.57), and 0.46 (0.41 to 0.52) (p < 0.0001 for all). It was also noted that when comparing vaccinated vs. unvaccinated patients, ORs were significantly increased for coronavirus and human metapneumovirus in vaccinated individuals (OR = 1.36 and 1.51, respectively; p < 0.01 for both).

The first study to explore virus interference among DoD personnel, the current investigation determined that influenza vaccination does not appear to increase risk of other respiratory viruses. Although findings showed that individuals receiving the flu vaccine were more likely to test as negative for pathogen detection and have lower risk of influenza (confirming a protective effect associated with vaccination), disease-specific testing indicated that vaccine-derived virus interference trends were significantly higher in relation to the coronavirus and human metapneumovirus. Additional testing is warranted to verify these effects. The current study benefited from a relatively large sample size, but was limited by a reliance on self-report to confirm vaccination status and the inability to establish a direct causal relationship between flu vaccination and respiratory viruses.

Source: Wolff GG. Influenza vaccination and respiratory virus interference among department of defense personnel during the 2017-2018 influenza season. Vaccine. 2020; 38: 350-354. DOI: 10.1016/j.vaccine.2019.10.1005.

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Posted June 4, 2020.

Angeline A. De Leon, MA, graduated from the University of Illinois at Urbana-Champaign in 2010, completing a bachelor’s degree in psychology, with a concentration in neuroscience. She received her master’s degree from The Ohio State University in 2013, where she studied clinical neuroscience within an integrative health program. Her specialized area of research involves the complementary use of neuroimaging and neuropsychology-based methodologies to examine how lifestyle factors, such as physical activity and meditation, can influence brain plasticity and enhance overall connectivity.

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