Dear Doctors: I went to our local pharmacy to get a flu shot for myself and also for my dad. It turns out that because he is 68 years old, he didn’t get the same vaccine as me. They gave him something called “fluad quadrivalent.” How is that different from the regular flu vaccine? Why did he need it?
Dear Reader: First, we want to thank you for taking an important step in safeguarding your health and that of your father. Flu season in the United States started early this year, and it is turning out to be particularly severe. It has resulted not only in widespread illness, but also in high rates of hospitalization. That makes getting vaccinated particularly important.
Due to age-related changes to the immune system, older adults are at increased risk of developing potentially life-threatening complications from a case of the flu. According to data collected by the Centers for Disease Control and Prevention in recent years, well over half of hospitalizations due to the flu, and up to 85% of flu-related deaths, have occurred in adults 65 and older. People of all ages who are living with underlying conditions such as diabetes, asthma, lung disease and heart disease are also at increased risk.
The good news is that this year’s flu vaccine is proving to be effective at reducing the severity of disease and decreasing the risk of hospitalization. By getting vaccinated, you and your dad are protecting yourselves, as well as the people around you.
To understand the difference between the shots you and your father received, we should first define a few terms. All flu vaccines contain something called an antigen. That’s a molecular structure found on the surface of viruses, including the influenza virus. When a virus infects the body, the antigens it contains act as an alarm bell. Their presence triggers the immune system to produce specialized proteins known as antibodies, which attack the invaders.
Flu vaccines work by teaching your immune system to recognize specific antigens. This primes the immune system to be ready with a strong protective response. Although your father got a different shot than the one you received, he did not get a different vaccine. Rather, he was given what is known as a high-dose flu vaccine. That’s a shot that contains the same antigens as the regular flu vaccine but is specially formulated to elicit a stronger immune response. At this time, several types of high-dose flu vaccines are approved for use in the U.S. Each one is formulated in a slightly different way, but all have the same effect -- that is, to rev up immune response.
The fluad quadrivalent shot that your father received contains something called an adjuvant. That’s an added compound that causes a markedly stronger immune response. Another high-dose flu shot, known as Fluzone High-Dose quadrivalent, achieves the same result by upping the quantity of antigens contained in the vaccine.
As with all flu shots, side effects can include soreness or swelling at the site of the injection, fever, muscle aches, headache or nausea. To locate a high-dose flu shot near you, visit vaccines.gov/find-vaccines.
(Send your questions to firstname.lastname@example.org, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)