14:43 PM

Asked and Answered – COVID-19, the Flu and Flu Shots


As we look into the future, there are many uncertainties. One of those is how the COVID-19 pandemic will look during flu season. Mark Knouse, MD, Chief, Lehigh Valley Health Network (LVHN) Division of Infectious Diseases, provided answers on how the two viruses stack up and the importance of receiving a flu vaccination.

Which virus is more contagious?

Right now, COVID-19 is more ‘contagious.’ This is mostly because of the lack of protective immunity in the regional population either through herd immunity (because of infection) or vaccination. Therefore, the relative contagiousness of COVID-19 may change over time as our community’s immunity changes.

Which illness has a greater risk for severe illness and complications?

Right now, COVID-19 is worse on average. It seems to cause viral pneumonia more often than the average seasonal flu and, as a result, more complications and higher death (mortality) rates. It also causes significant heart and stroke risks.

How are the symptoms different?

Initial symptoms are remarkably similar and overlap a lot – it will be a big challenge to distinguish the two diseases in the fall if both are circulating together. COVID-19 causes viral pneumonia more often than influenza, but the flu can do that as well. Loss of taste and smell seems to be more common with COVID-19.

When should people get their flu shots?

Early fall is likely the best time – late September or early to mid-October. Remember, it is never too late to get a flu shot, as cases often extend into early spring. Vaccination against seasonal flu will be more critical than ever if COVID-19 hits hard again. It will help prevent hospitals and health care systems from becoming overwhelmed.

Why is it important to receive a flu shot?

Influenza can cause mild to severe illness. For some people, it is life threatening. According to the Centers for Disease Control and Prevention (CDC), during the last flu season between 24,000 and 62,000 people died as a direct result of this illness in the United States.

Every year, the CDC receives and tests thousands of influenza viruses from around the world and collaborates with other World Health Organizations. The CDC presents information to the Food and Drug Administration (FDA) advisory committee, who ultimately decides which viruses the vaccination will address. The flu vaccine is the best way to protect yourself and reduce the spread of this virus in our community.

How will this fall’s flu season be different than those in the past?

There will be heightened concerns when both viruses may be circulating. But we really don’t know what to expect from each flu season until it occurs (much like the coronavirus).

It’s possible that the isolation and distancing measures for the coronavirus might actually result in a ‘better’ flu season with fewer cases. So far, information from the southern hemisphere suggests a much lower number of influenza cases than the last several years combined. We are hopeful that this will be similar during our flu season in the northern hemisphere.

Will COVID-19 tests and flu tests be able to detect the difference between the two viruses?

Yes, absolutely! Most of the tests that we will be using this fall will be nucleic acid tests (NAT for short). The majority of NAT tests use PCR (polymerase chain reaction) technology. This technology detects very specific gene sequences of a virus. We are planning to use a single (multiplex) test, which will look for RSV, Influenza A and B, and COVID-19 in each specimen.

Alternatively, if the volume of test requests exceeds our capacity, we may use combinations of separate NAT tests for these viruses. The tests are extremely accurate at distinguishing between the two viruses. They will not ‘label’ an influenza virus as a COVID-19 virus or vice-versa. In other words, there is an extremely low likelihood of a false positive. Tests may provide a false negative result if there is insufficient material, poor specimen/site choice, if someone receives the test too early (before symptoms) or is tested too late.

Is it possible to get sick from the flu shot?

No, flu vaccines do not cause flu illness. The most common type of vaccination is the flu shot, which contains a killed virus. The nasal spray flu vaccine contains weakened (attenuated) viruses, so that they will not cause flu illness. The weakened viruses are cold-adapted, which means they are designed to only multiply at the cooler temperatures found within the nose, and not the lungs or other areas where warmer temperatures exist. You cannot get the flu from these immunizations.

If I get a flu shot, can I still get the flu?

The flu shot is critical to protecting yourself and your community during flu season. But protection is never 100%, and some people can still get the flu after being vaccinated. How well the flu vaccine works (or its ability to prevent influenza illness) can range greatly depending on the person being vaccinated.

In general, the flu vaccine works best among older children and healthy adults. The elderly population and people with certain chronic illnesses might develop less immunity than healthy young adults after vaccination. However, even for these high-risk individuals the flu vaccine still can provide protection against getting severe complications from the flu. Also, the more people vaccinated in a group, the better herd immunity among the group. This provides better protection for those who cannot build immunity themselves.

Influenza vaccines protect against infection and illness caused by the viruses in the vaccine that research indicates will be most common this season. Even if the match is not exact there may be cross-protection provided by the vaccine against similar strains. Although vaccines can't be guaranteed to be 100% effective against influenza, they still afford you a much greater chance to avoid infection and illness than you would otherwise have.

Where can I get a flu shot this year?

LVHN has established flu shot clinics throughout the region. Visit LVHN.org/flushot to find an event near you. Can’t make it to a flu shot clinic? Don’t worry. You can call your primary care provider to schedule your flu vaccination or visit any ExpressCARE location without an appointment.