Did flu shots and pneumococcal vaccines offer some COVID-19 protection?

As the coronavirus disease 2019 (COVID-19) pandemic moved into the traditional influenza season, there was a strong drive to administer the flu shot to as many children as possible, to help prevent the health care system from having to fight 2 diseases at the same time. A report in Cureus discusses whether getting that flu shot would have a protective effect on the COVID-19 course.¹

The investigators conducted a retrospective electronic chart review on all patients aged 20 years and younger who were positive for COVID-19, verified by polymerase chain reaction testing and had been seen at the Arkansas Children’s Hospital System between February 1, 2020 and August 30, 2020. Patients who had received the killed influenza vaccine during the 2019-2020 flu season were considered to have been flu vaccinated for the purpose of the study. Previous flu shots were not taken into account. A patient was considered to have been given the pneumococcal vaccine if he or she had been administered a full age-appropriate vaccine course. Severity of illness was divided into 5 categories: asymptomatic, mild, moderate, severe, and critical.

A total of 905 patients were included in the final cohort and had a complete record. In this cohort, 62.51% were found to have an asymptomatic disease course. Among those who were symptomatic, 33.20% had mild disease; 3.37% had moderate disease; 0.61% had severe disease; and only 0.31% had critical disease. The researchers found that the patients who had been vaccinated for influenza had lower odds of symptomatic disease than the patients who hadn’t been vaccinated (adjusted odds ratio [aOR]=0.714, 95% CI [0.529, 0.964], p=0.028). A similar effect was seen in patients who had been vaccinated for the pneumococcal vaccine (aOR=0.482, 95% CI [0.277, 0.837], p=0.010). Lower odds of respiratory symptoms were seen in patients with a flu shot (aOR=0.678, 95% CI [0.492, 0.934], p=0.018), but no difference was found in patients with the pneumococcal vaccine versus those who didn’t have it. Additionally, having the flu shot also led to lower odds of having severe disease (aOR=0.672, 95% CI [0.500, 0.903], p=0.008) and a similar effect was seen with those who had the pneumococcal vaccine (aOR=0.412, 95% CI [0.234, 0.725], p=0.002).

The researchers concluded that both the seasonal influenza and pneumococcal vaccine could provide a protective value against symptomatic COVID-19 disease. They urged further study to understand how the influenza and COVID-19 can impact a virus’s epidemiology.

Reference

1. Patwardhan A, Ohler A. The Flu vaccination may have a protective effect on the course of COVID-19 in the pediatric population: when does severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) meet influenza?. Cureus. 13(1): e12533. doi:10.7759/cureus.12533