Doctors' opinions on a major flu shot misconception

Many people consider skipping their annual flu shot due to busy schedules, needle anxiety, or other reasons. However, a common misconceptionthat the vaccine can give you the fluremains widespread and misleading, according to medical experts. This myth frustrates healthcare professionals, who work hard to clarify how flu vaccines truly function.

This is probably the question I hear most about the flu vaccine, and it may contribute to low immunization rates, said Paul Offit, director of the Vaccine Education Center at Childrens Hospital of Philadelphia. Indeed, flu vaccination rates have dropped in recent years, with less than half of adults receiving the shot during the 2023-2024 flu season.

Influenza is a respiratory illness caused primarily by influenza A and B viruses. Each year, these viruses evolve, producing new strains that spread globally. Flu season in North America generally spans from October to May, affecting millions of people. In the U.S. during the 2024-2025 season, estimates suggest 610,000 to 1.3 million hospitalizations and 27,000 to 130,000 deaths from the flu.

Scientists monitor viral mutations months in advance to design vaccines that target the most prevalent strains. Most flu vaccines contain inactivated virus particles or proteins, known as antigens, which prime the immune system to recognize and combat the virus.

The immune system is like an army. You wouldnt send soldiers into battle without training. The flu vaccine teaches the body which viral components to focus on, explained Walter Orenstein, professor emeritus at Emory School of Medicine and former director of the U.S. Immunization Program at the CDC.

Because the vaccines contain only viral proteins, not live viruses, they cannot cause influenza. Some people may experience mild symptoms such as fatigue, low-grade fever, or muscle aches, which result from the immune system activating and producing antibodies.

One type of flu vaccine, the nasal spray, uses a weakened live virus. While it cannot cause full-blown flu, it may trigger mild respiratory symptoms like a runny nose or cough. When someone says they caught the flu from the vaccine, its actually an immune response, not the flu itself, Offit noted.

It takes roughly two weeks after vaccination to build sufficient immunity. If a person contracts influenza shortly after getting the shot, it is usually due to prior exposure to the virus or incomplete protection from the vaccine. Effectiveness varies yearly, generally ranging from 40% to 60% against infection. Immunity may also wane after six months, which is why annual vaccination is recommended.

Who Should Get Vaccinated?

The CDC recommends flu vaccination for everyone six months and older, with exceptions for individuals who have severe allergic reactions to the vaccine. Different vaccine types are available:

• Standard (trivalent) vaccine: Protects against three virus strainstwo influenza A strains and one influenza B strain.
• High-dose vaccine: Contains up to four times the antigen amount of standard vaccines; ideal for adults 65+ and immunocompromised individuals.
• Adjuvanted vaccine: Includes immune boosters called adjuvants to strengthen the bodys response.
• Recombinant vaccine: Stronger than standard vaccines and produced without using flu virus or chicken eggs.
• Nasal spray vaccine: Contains a weakened live virus that replicates only in the cooler temperatures of the nose; safe for most healthy individuals but not recommended for pregnant or immunocompromised people.

In summary, flu vaccines do not cause influenza. Temporary side effects like low-grade fever and body aches may occur, and it is possible to catch the flu after vaccination. Vaccines aim to reduce the severity of illness, hospitalizations, and deaths rather than guaranteeing complete prevention.

Understanding the Flu Vaccine: Separating Fact from Fiction

The annual flu vaccine is a critical tool in preventing widespread illness, yet misconceptions about its effectiveness and safety persist. One of the most common myths is that the flu vaccine itself can cause the flu. Medical experts, however, have consistently debunked this claim. Flu vaccines contain inactivated viruses or viral proteins, which cannot cause the flu. What some perceive as "catching the flu" post-vaccination is typically a mild immune response, not the flu virus itself. This misunderstanding is one of the main barriers to higher vaccination rates, as evidenced by the continuing decline in flu vaccine uptake in recent years.

It's essential to highlight that while flu vaccines are not foolproof, they significantly reduce the risk of severe illness, hospitalizations, and death. The effectiveness of the vaccine can vary each year, but it remains a critical line of defense, especially for vulnerable populations such as the elderly and immunocompromised individuals. With flu season being particularly dangerous, especially in North America, the importance of vaccination cannot be overstated. Each year, flu-related complications result in thousands of hospitalizations and deaths, and the flu shot remains one of the most effective ways to mitigate this toll.

Despite the ongoing myths, the medical community continues to stress the importance of getting vaccinated. As flu viruses mutate and evolve, scientists work tirelessly to ensure that the vaccine targets the most prevalent strains. The choice not to vaccinate is not just a personal one; it affects public health as well. By opting for vaccination, individuals contribute to herd immunity, ultimately helping to protect the most vulnerable in our society.

Sources:

• What doctors say about one of the biggest flu shot myths