Houston Methodist. Leading Medicine.
Houston Methodist. Leading Medicine

Flu Shots

What's in a flu shot?
Chicken eggs are used in the production of the vaccine. The influenza viruses used in the vaccine are grown in hens' eggs.

Why get a flu shot?
To prevent much of the illness and death caused by influenza. In the United States, influenza usually occurs from about November until April, with activity peaking between late December and early March. The optimal time for vaccination is usually the period from October to mid-November. However, to avoid missed opportunities for vaccination, vaccines are often offered starting in October and continuing through the winter. It takes about 1 to 2 weeks after vaccination for antibodies against influenza to develop and provide protection.

Can a flu shot give you the flu?
The influenza vaccine produced in the United States that is given as a shot, cannot cause influenza. The only type of influenza vaccine that has been licensed in the United States is made from killed influenza viruses, which cannot cause infection.

Who should get one?
Influenza vaccine is specifically recommended for people who are at high risk for developing serious complications as a result of influenza infection (Centers for Disease Control and Prevention and the American Academy of Family Physicians, 2000 recommendations).

These high-risk groups include:

  • all people aged 50 years or older
  • people of any age with chronic diseases of the heart, lung or kidneys, diabetes, immunosuppression, or severe forms of anemia

Other groups for whom vaccine is specifically recommended are:

  • residents of nursing homes and other chronic-care facilities housing patients of any age with chronic medical conditions
  • women who will be more than 3 months pregnant during the influenza season
  • children and teenagers who are receiving long-term aspirin therapy and who may therefore be at risk for developing Reye syndrome after an influenza virus infection

Influenza vaccine is also recommended for people who are in close or frequent contact with anyone in the high-risk groups defined above.

These people include:

  • health care personnel and volunteers who work with high risk patients
  • people who live in a household with a high-risk person

Who shouldn't get one?

  • Children under 6 months old
  • Individuals with allergies to eggs (chicken eggs are used in the production of the vaccine)
  • Anyone with an allergy to Neomycin, or Thimerosol (a preservative present in contact lens solutions and the flu vaccine)

What are the benefits?

  • Studies of healthy young adults have shown influenza vaccine to be 70% to 90% effective in preventing illness
  • In the elderly and those with certain chronic medical conditions, the vaccine is often less effective in preventing illness than in reducing the severity of illness and the risk of serious complications and death
  • Studies have shown the vaccine to reduce hospitalization by about 70% and death by about 85% among the elderly who are not in nursing homes
  • Among nursing home residents, vaccine can reduce the risk of hospitalization by about 50%, the risk of pneumonia by about 60%, and the risk of death by 75% to 80%

What are the risks?
While influenza vaccine, like any other vaccine or medicine, is capable of causing serious problems such as severe allergic reactions, the risk of the vaccine causing serious harm, or death, is extremely small. Almost all people who get influenza vaccine have no serious problems from it.

The most common side effect from influenza vaccination is soreness at the site of the injection. The soreness can last up to 2 days but is usually mild and does not affect a person's ability to perform their normal daily activities. Some people, usually children who have not been exposed to influenza virus in the past, may have fever and body aches after vaccination. These symptoms, if they occur, usually start 6-12 hours after vaccination and can continue for 1 or 2 days.

Less common side effects that can occur after vaccination include allergic reactions and Guillain-Barré syndrome (GBS), a severe paralytic illness. Life-threatening allergic reactions are very rare, but can happen in people who have severe allergy to any vaccine component, most commonly allergy to eggs. The influenza viruses used in the vaccine are grown in hens' eggs. People who have an allergy to eggs or who have ever had a serious allergic reaction to a previous dose of influenza vaccine should consult with a doctor before getting an influenza vaccination.

If there is a risk of GBS from current influenza vaccines, it is estimated at 1 or 2 cases per million persons vaccinated - much less than the risk of severe influenza, which can be prevented by vaccination.

Why sponsor workplace flu shots?
Influenza related costs are a result of:

  • absenteeism, replacement & overtime costs
  • interruption of service and/or product delivery
  • lost or reduced sales and productivity
  • health benefit costs

The Flu virus thrives in the typical office environment, and will infect almost one in four workers each winter.

Each victim will be absent for 3-5 days, and individual productivity can be adversely affected for up to two weeks following an infection.

Each infected employee will pass the virus to coworkers, family members, and their community at large, including vulnerable high risk individuals.

** Each vaccination dramatically improves anyone's chances for a flu free winter, and can contribute significant financial savings to participating companies.

Research information includes:
B.C. Hydro posted savings of $160,000 in one year, and other companies participating in occupational health vaccination programs have included Mercedes-Benz, Northern Telecom, Costco, and Greyhound.