University HealthCare Alliance

September 25, 2020

Flu Vaccination in the Time of COVID-19

It’s time to get a flu shot. In a Q&A, Shanthi Kappagoda, MD, clinical associate professor of infectious diseases, explains why it’s especially important to be vaccinated this year.

In this year of shuttered schools, empty restaurants, mask wearing and hand sanitizing, nearly all the inoculation talk has centered on the development of a coronavirus vaccine: When will it be ready so we can get back to normal? 

Thinking about the flu shot may seem trivial by comparison.

But Shanthi Kappagoda, MD, a clinical associate professor of medicine who cares for patients at Stanford Health Care’s Infectious Disease Clinic, says that it’s critical to be vaccinated against the flu this year to stay as healthy as possible during the pandemic, protect people who are vulnerable and keep hospitals from being inundated with both flu and COVID-19 patients. The flu season peaks from December through February in the United States sickens between 9 million and 49 million people each year, and sends an average of 200,000 to the hospital annually, according to the Centers for Disease Control and Prevention.

Associate editor Mandy Erickson recently reached out to Kappagoda to get her thoughts on the convergence of flu season and the COVID-19 pandemic.

1. Why is it important to get a flu shot when everyone’s social distancing?

Unfortunately, I don’t think everyone is social distancing. There is still a risk of getting the flu this year, especially with the holidays coming up. 

The flu is most dangerous for older adults and young children. By being vaccinated, you are not just protecting yourself; you are also protecting other people you may come into contact with, including people who are not able to get the vaccine.

In addition, every fall and winter, hospitals see an increase in patients because of the flu, and there’s concern they will become overwhelmed with COVID-19 and flu patients. 

2. Do we know the risks of having flu and COVID-19 at the same time? 

There have been only a handful of reports in medical literature about patients infected with SARS-CoV2, the virus that causes COVID-19, and an influenza virus at the same time. Several patients ended up in intensive care, but because the numbers are so small, and most reports are on hospitalized patients and not outpatients, I don’t think we know enough about this topic yet to draw any conclusions.

3. How do the flu and COVID-19 differ?

As far as symptoms, loss of taste and sense of smell appears to be more common with COVID-19 than with influenza, but it’s important to know that not everyone with COVID-19 notices a change in their sense of taste or smell. 

Other important differences relate to transmission, which is why it has been so hard to control COVID-19. The period of time that you are infectious appears to be longer with COVID-19 than with influenza. With a flu, people typically become contagious about a day before they have symptoms and remain contagious for about seven days after symptoms start. With COVID-19, our best estimate is that you can become infectious about two days before symptoms start, and remain contagious for up to 10 days afterward, although new information is coming out on this topic frequently.

There also appears to be a greater number of asymptomatic COVID-19 cases than asymptomatic flu cases. And the death rate for COVID-19 appears to be higher than the death rate for flu. There also appears to be more super-spreading events with COVID-19 than with flu: It seems to be transmitted more easily through the air, although both viruses are primarily spread by droplets. Finally, the risk of complications and death in healthy infants and children appears to be higher for flu than for COVID-19.

4. Is COVID-19 changing anything about this year’s flu vaccine?

The flu vaccine was developed this year in the same way it’s developed every year. The four strains of influenza that are going into this year’s flu shot were decided on in March, and the vaccine was distributed starting this month. I think it is unlikely that vaccinating for flu would cause any shortages or changes to the rollout of a COVID-19 vaccine. 

Given concerns about an overburdened hospital system this fall and winter with admissions for both COVID-19 and influenza, an increased amount of flu vaccine is being made. The CDC reports that there will be 194 million to 198 million doses of flu vaccine available for this season, which is a record number. Unfortunately, only about 40% to 50% of adults in the United States get the vaccine, with rates commonly lower among low-income people and people of color — those most impacted by COVID-19.

5. Why do we need to get a flu shot every year? 

The antibodies your immune system makes in response to the vaccine last only about six months. But also, influenza is a very tricky virus. Individual strains circulating in the community switch from year to year, so the vaccine from last year may not contain the strains that are circulating this year. In addition, individual strains of the virus constantly mutate, enabling them to evade our immune system and cause disease.

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