Is It Possible to Prevent Flu in Adults?
- Limit touching high-touch surfaces where flu viruses may remain alive; examples include handrails, doorknobs, faucets, keyboards, and elevator buttons.
- Wash your hands often, especially after touching high-touch surfaces, being in public places, or at work.
- Avoid touching your eyes, nose, or mouth before washing one's hands.
- Avoid close contact with people who appear ill.
- Do not share clothes or other personal items with another person during a flu outbreak.
- Those infected with influenza should stay at home for 24 hours after fevers have resolved.
The best means of preventing the flu is getting an influenza vaccination. The CDC recommends an annual flu vaccine for everyone 6 months of age and older.
Two general types of vaccines are available:
- One is the injectable vaccine (known as the flu shot) made from inactivated virus. The flu shot contains only killed influenza viruses A and B. The other is a live attenuated influenza virus, or weakened, vaccine (LAIV) that health care providers squirt into the nose. This is the intranasal vaccine or nasal spray vaccine.
- The intranasal form is indicated for certain people who may prefer it to a shot, and it is approved for people from 2 through 49 years of age. Doctors do not recommend it for people who are immuno-suppressed or have other conditions (see below for a list).
There were concerns about poorer effectiveness against H1N1 flu virus than injected vaccines, and the Advisory Committee on Immunization Practices (ACIP) recommended against its use during flu seasons in 2016-17 and 2017-18. Since 2018-19, the LAIV (FluMist) includes an H1N1 component, and the ACIP and the CDC recommend it along with all of the other flu vaccines.
There are different injected flu vaccines, such as the quadrivalent flu shot, which contains two type A viruses and two type Bs, rather than the standard trivalent that has two type As and one type B:
- There is a high-dose shot formulation for people over 65 years of age and an intradermal (into the skin) version for people ages 18-65, and it uses a tiny needle.
- There is also a flu vaccine licensed for people age 65 and over that contains an adjuvant (an added immunity booster). This vaccine (Fluad) may produce higher levels of flu antibodies and may offer greater protection. In August 2014, the FDA approved Afluria (as both a trivalent and a quadrivalent formula), which is injected into the muscle through a needle-free jet injector. Medical professionals approve Afluria for ages 18-64.
At this time, there is no hard evidence that one vaccine is better than any other. The ACIP and the CDC have not made any recommendations of specific flu vaccines. The most important thing is that people get whichever flu vaccine is available or is recommended by their health care professional. People can find a complete listing of currently available flu vaccines at http://www.immunize.org/catg.d/p4072.pdf.
An important point is that no one vaccine is recommended over the others and one should not delay vaccination in order to wait for one of the others if there is a vaccine available.
It is also important to note a widely circulated study that reported a weak, inconclusive link of flu vaccination with miscarriage; in essence, there was a slightly higher number of miscarriages in a group of women who received flu vaccine compared to usual, but there was no evidence that the vaccine caused this. Because the risk of serious flu complications and death during pregnancy is clear and far higher, the American College of Obstetricians and Gynecologists (ACOG) recommends flu vaccination as an essential part of prenatal care.
Lastly, research has shown that flu vaccination is safe in most people who have all but the most severe egg allergy. People who can eat lightly cooked eggs, for example, are not likely to be allergic to eggs. People who have only experienced hives after exposure to eggs can receive any of the licensed flu vaccines that approved for their age and health. They may also receive the vaccine at any facility licensed to give it, such as a local pharmacy or health fair.
People who have had reactions more severe than hives after eating eggs may receive any licensed flu vaccine, but they should receive it in a facility that is staffed with health professionals and equipped to manage severe allergic reactions. This need not be a doctor's office or hospital, nor is there a prescribed 30-minute observation period after receiving the vaccine.
Health professionals giving vaccines to anyone should be able to recognize severe allergic reactions. Symptoms and signs of a severe allergic reaction may include:
- Throat or tongue swelling
- Repeated vomiting
- Difficulty breathing, and may require the use of epinephrine or emergency medical treatment
Health care providers administer the influenza vaccine every year prior to flu season. Immunity to the flu virus develops after about 2 weeks. The CDC recommends that vaccine administration as soon as it becomes available each fall.
- Because of substantial vaccine distribution delays during previous influenza seasons and the possibility of similar delays in the future, medical professionals recommended that anyone at high risk for complications from the flu get a flu shot as early as September. This same group of people can still get the vaccine throughout the flu season if they were unable to obtain vaccination earlier.
- While there is some data suggesting that flu vaccine antibodies drop a small percentage in older individuals after a few months, there is no evidence that this lowers the effectiveness of the vaccine if given early before flu season. Even if antibody levels drop, immune memory cells can ramp up antibodies very quickly if you are exposed to flu.
- Vaccination reduces the risk of flu illness by 40%-60% during seasons when the circulating flu viruses are well-matched to the flu vaccine. Flu vaccines tend to work better against influenza B and influenza A(H1N1) viruses and offer lower protection against influenza A(H3N2) viruses.
- In some years, the vaccine is less effective because the circulating flu virus genetically changed from the ones that were anticipated and included in the vaccine. The H3N2 strain mutates more often and more quickly than other strains. The 2014-15 flu vaccine was only 23% effective due to changes in the circulating flu virus that season.
- Not only does the flu vaccine decrease the risk of getting flu infection, but it can also decrease the number of visits to a doctor's office, lost work days, hospitalizations, and risk of death from the flu virus.