What to Expect for Flu Season 2023-24

The 2023–24 influenza season brings renewed attention to the importance of vaccination and workplace infectious disease control. With the potential for co-circulating respiratory viruses, employers must stay proactive in protecting their workforce. This fact sheet outlines what to expect this flu season, current vaccine guidance, and effective prevention measures employers can implement to maintain productivity and reduce illness-related absences.

Influenza, a contagious respiratory illness, is annually associated with local sickness outbreaks and disruptive work and school absences. Flu tends to spread more rapidly during the winter in cold, dry conditions when there is less sunlight and people spend more time indoors.

Vaccination

Flu vaccination is the first line of defense recommended by public health officials. In a single season, vaccination was found to prevent an estimated 1.8 million illnesses, 1 million medical visits, 22,000 hospitalizations and nearly 1,000 deaths, according to the Centers for Disease Control and Prevention (CDC).

Vaccination helps prevent the spread of illness to family members, co-workers and vulnerable populations such as the elderly, infants and people with medical conditions who have a higher risk of serious complications such as pneumonia. The more people who get vaccinated, the greater the protection afforded to everyone.

Vaccine composition is based on strains that predominate during alternating flu seasons in the northern and southern hemisphere, as well as research on emerging strains. The 2023-24 quadrivalent (four component) seasonal influenza vaccine formula targets two influenza A viruses and two influenza B viruses.

Vaccine manufacturers project that they will supply Americans with 156.2 million to 170 million doses for the 2023-2024 season. Most will be thimerosal-free or thimerosal-reduced vaccines (91 percent), and about 21 percent will be egg-free. (See sidebar on Page 2.) Thimerosal, an organic compound containing mercury, is widely used as a preservative in biological and drug products.

The vaccine causes protective antibodies to develop in the body about two weeks after vaccination. Although any type of vaccine is not 100 percent preventive, getting vaccinated can reduce illness duration and severity.

Some licensed vaccines are not recommended for certain groups of people. For example, this season the CDC recommends specific products for people over 65 – Fluzone high-dose, Flublok recombinant and Fluad adjuvanted – because they are potentially more effective than standard-dose inactivated influenza, recombinant influenza or live attenuated influenza vaccines recommended for people under age 65. (Refer to this summary of flu vaccine recommendations for details.)

Symptoms and Treatment

Most people who get the flu have mild-to-moderate illness and recover on their own, but influenza can cause serious complications and death in vulnerable populations.

Symptoms may include fever/chills, cough, shortness of breath, runny nose or congestion, achiness, headache and fatigue. Some people, especially children, may have vomiting and diarrhea. This season, it’s advisable to get tested for COVID-19 because many, but not all, symptoms are similar to the flu. (Refer to Table 1 on page 3.)

Flu remedies include rest, staying hydrated and eating nourishing foods. Over-thecounter medications are available to help relieve symptoms. Antiviral drugs may be prescribed in certain cases to treat symptoms and shorten illness duration. Studies show that antiviral drugs work best for treatment when started within two days of getting sick, although starting them later can still be helpful. Flu antiviral drugs are not used to treat COVID-19.

Most people who get the flu recover within five days to two weeks. Some people may develop sinus and ear infections, and in serious cases, pneumonia, inflammation of the heart, brain or muscles, or organ failure. More About Prevention Along with vaccination, contagious disease prevention measures employers can recommend to employees include:

• Frequent hand washing with soap and water
• Using hand sanitizer when water is not available
• Covering coughs and sneezes and throwing tissues away
• Disinfecting shared objects and communal areas
• Not touching one’s nose, mouth and eyes
• Staying home when ill and avoiding others who are sick
• Wearing a mask, especially when in public places

Employers may consider promoting flu prevention in the workplace with:

• Posters and flyers
• Communications from leadership
• Onsite health fairs
• Social media channels
• Vaccination during work hours
• Referrals to flu shot providers (WorkCare can assist with this)

Legal Considerations

Employers have the right to establish health and safety rules that are job-related and consistent with business necessity. This includes requiring immunizations that protect against the spread of infectious illnesses. Employers who require vaccinations are expected to engage in an interactive process to comply with the Americans with Disabilities Act (ADA), including exemptions for medical necessity or religious beliefs. State laws require health care facilities to ensure consenting employees receive influenza vaccines. In some workplaces, infectious disease management includes mandatory use of personal protective equipment such as gloves, gown, mask, eye protection, face shield and safe injection practices. Surgical masks or respirators may be used to help reduce the spread of disease via airborne or droplet contamination.

Table 1: COVID-19 and Flu Symptom Comparison

COVID-19 symptoms	Flu symptoms
Fever or chills Cough Shortness of breath or difficulty breathing Fatigue Muscle or body aches Headache New loss of taste or smell Sore throat Congestion or runny nose Nausea or vomiting Diarrhea	Fever* or feeling feverish/chills Cough Sore throat Runny or stuffy nose Muscle or body aches Headache Fatigue Some people may have vomiting and diarrhea; more common in children than adults. * Not everyone with flu will have a fever.

Changes for People With an Egg Allergy

Most flu vaccines are produced using an egg-based manufacturing process. This season, the CDC has advised people with egg allergies that it’s safe to receive either an egg-based or non-egg-based vaccine approved for their age and health status. A qualified medical professional can advise recipients who are unsure about which vaccine to receive. In prior seasons, people with a severe egg allergy other than hives were advised to be vaccinated in an inpatient or outpatient medical setting. However, because severe reactions can occur with any vaccine, the CDC says all vaccines should be administered in settings in which personnel and equipment needed for rapid recognition and treatment of acute hypersensitivity reactions are available. Severe reactions are rare.

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