#16,463
- A little over a year ago, in PHE Study: Co-Infection With COVID-19 & Seasonal Influenza, we looked at a Public Health England study that warned that being co-infected with influenza and COVID more than doubled the risk of death over having COVID alone.
- More recently, in Clinical and virological impact of single and dual infections with influenza A (H1N1) and SARS-CoV-2 in adult inpatients, coinfection was linked to increased odds of acute kidney injury, acute heart failure, secondary bacterial infections, multilobar infiltrates and admittance to ICU than monoinfection.
For now, we mostly have animal studies, and one of the most recent is a ferret study that finds that coinfection with influenza and COVID increases the severity of illness in these lab animals, and that receipt of the flu vaccine prior to infection - even when it doesn't prevent infection - can help ameliorate the severity of illness.
SARS-CoV-2 and Influenza A virus Co-infections in Ferrets
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and seasonal influenza viruses are co-circulating in the human population. However, only a few cases of viral co-infection with these two viruses have been documented in humans with some people having severe disease and others mild disease. In order to examine this phenomenon, ferrets were co-infected with SARS-CoV-2 and human seasonal influenza A viruses (IAVs) (H1N1 or H3N2) and were compared to animals that received each virus alone.
Ferrets were either immunologically naïve to both viruses or vaccinated with the 2019-2020 split-inactivated influenza virus vaccine. Co-infected naive ferrets lost significantly more body weight than ferrets infected with each virus alone and induced more severe inflammation in both the nose and lungs than ferrets single-infected with each virus.
Co-infected naïve animals had predominantly higher IAV titers than SARS-CoV-2 titers, and IAVs efficiently transmitted to the co-housed ferrets by direct contact. Comparatively, SARS-CoV-2 failed to transmit to the ferrets that co-housed with co-infected ferrets by direct contact.
Moreover, vaccination significantly reduced IAVs virus titers and shortened the viral shedding, but did not completely block influenza virus direct contact transmission. Notably, vaccination significantly ameliorated the influenza associated disease by protecting vaccinated animals from severe morbidity after IAV single infection or IAV and SARS-CoV-2 co-infection, suggesting that seasonal influenza virus vaccination is pivotal to prevent severe disease induced by IAVs and SARS-CoV-2 co-infection during the COVID-19 pandemic.
Just over a week ago, in Preprint: Antigenic & Virological properties of an H3N2 Variant That Will Likely Dominate the 2021-2022 Influenza season, we looked at a report that suggested this year's flu vaccine will likely be less effective in preventing infection than originally hoped.
While a `mismatch' between the vaccine component and the H3N2 virus currently circulating is less than ideal, the vaccine is still expected to reduce the severity of one's illness if they are infected.
Given the challenges that lie ahead, I'm glad I got the flu vaccine last September, and will gladly take whatever level of protection it offers.
That, combined with getting the COVID vaccine and booster, wearing face masks in public, and practicing good hygiene, should increase my odds of coming through the next few months relatively unscathed.
But if it doesn't, at least I'll know I did everything I reasonably could to prevent a bad outcome.
