“In some areas of the Southern Hemisphere South Africa and Australia in particular they have had very mild flu seasons,” said Leonard A. Mermel, DO, ScM, AM (Hon), FSHEA, FIDSA, FACP, medical director of Epidemiology and Infection Control at Rhode Island Hospital in Providence. “Masking, staying at home, avoiding large crowds, not going to work when sick some of these things that are happening with COVID-19 are going to tamp down transmission of influenza.”

The role of vaccine efficacy in this flu reduction was not discussed at a recent press conference held by the Infectious Diseases Society of America. That may become more clearly understood in the U.S. 2020-2021 flu season, which has created a similar vaccine but does not see the compliance levels with masking reported in other countries.

“We have not rounded the corner in terms of COVID-19. Although there are some positive signs in terms some states getting some things under control,” said Jeanne Marrazzo, MD, MPH, FIDSA, an infectious diseases professor at the University of Alabama at Birmingham. “Overall, we are still on a razor’s edge with regard to COVID-19.”

Mutable influenza is infamous for its unpredictably, thus the old adage, “If you have seen one flu season, you have seen one flu season.”

“The reasons for that are myriad, but really relate to our ability to predict the antigenic components of the virus,” said Marrazzo. “Can we get ahead of the game and choose the appropriate constituents for the vaccine?”

Vaccine Components

The Centers for Disease Control and Prevention recently announced that the components for the 2020-2021 egg-based vaccines include:

  • hemagglutinin (HA) derived from an influenza A/Guangdong-Maonan/SWL1536/2019 (H1N1)pdm09-like virus;
  • influenza A/Hong Kong/2671/2019 (H3N2)-like virus;
  • influenza B/Washington/02/2019 (Victoria lineage)-like virus, and (for quadrivalent egg-based vaccines);
  • influenza B/Phuket/3073/2013 (Yamagata lineage)-like virus.

“Sometimes we [match the viruses] well, sometimes not so well,” Marrazzo said. “For example, last year we had two waves of influenza A that were pretty significant. A lot of people die from the flu every year. The other concern is that last year, for example, some places experienced somewhat unexpected outbreaks of influenza B, which had a predilection for kids. So here in Alabama and a lot of other places, we had to shut down some schools because of influenza.”

There are some testing panels that can detect both flu and SARS-CoV-2 rapidly, but ensuring an adequate supply could be an issue, Mermel said. This is a critical issue because both flu and COVID-19 present with similar symptoms of fever, cough, and fatigue. However, COVID-19 also can cause a loss of taste and smell.

“A differentiated complication is that COVID can form blood clots in veins and arteries,” he said. “In terms of the spectrum of illness, both can be asymptomatic, mild to quite severe.”

Although the signs from the Southern Hemisphere may bode well, both speakers stressed it is absolutely critical to get a flu vaccine this year even for those who typically avoid it. “The big concern this year is that we are going to see what could be a perfect storm of accelerated COVID-19 activity, as people gather more inside, and as they become continually fatigued with the mask wearing, the social distancing, and the hand hygiene [then] they are exposed to seasonal influenza,” Marrazzo said.

There is the possibility of coinfection or that influenza could weaken the immune system enough to make a COVID-19 particularly serious. “We really can’t be complacent about this,” she said. “People really need to take the flu vaccine seriously. It does work it prevents symptomatic illness, hospitalizations, and mortality. If there is ever a year to get your flu vaccine and get your kids vaccinated, this is the year.

“It can be a very serious disease. Nine million to 45 million individuals in the United States are infected with seasonal influenza every year, leading to 140,000 to 800,000 hospitalizations, and, in the United States, 12,000 to 60,000 deaths,” Mermel said.

There are similar findings with flu and COVID-19 adversely affecting disadvantaged communities, so a flu immunization effort should target these populations.