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Column originally published Nov 12, 1997
Column last revised/updated on Jun 22, 2019

Influenza Vaccine Is Very Important For Seniors, And Those With Chronic Medical Conditions

Question: Our son has asthma. Last time when we saw our family doctor for a follow-up visit, she told us that we should all get the flu shot. We have heard from our friends that flu shot sometimes can make us sick, and it is only recommended for seniors. Is this true? If we get the flu shot, can we deprive the seniors of this vaccine?


I agree with your doctor that your family, especially your son, can benefit from the flu shot. Let me begin by explaining about influenza and its complications, and how to prevent it.

Influenza is a virus infection that begins in the nose and throat, causing sore throat and nasal congestion. Very quickly the virus spreads to the blood, and causes fever, chills, headache, tiredness, and aching all over. There is often some cough, pain in the abdomen, nausea and vomiting.

In healthy individuals, influenza symptoms usually last 3 to 7 days. With rest, lots of fluids, and acetaminophen (but not aspirin), influenza is often a mild to moderate illness. In North America, influenza usually occurs in winter as epidemics, causing school closure when large numbers of students are sick at home.

For seniors over 65 years of age, and those with underlying medical conditions, influenza can cause complications like pneumonia and deterioration of their medical conditions. Influenza is the most common cause of pneumonia and death for seniors.

There are two groups of influenza virus: A and B. Both of them change their internal structure regularly. As a result, immunity to one strain of influenza will not protect a person against another strain. Therefore, immunity against influenza, whether from a previous infection or immunization, does not work very well from year to year.

Around the world, many laboratories are tracking influenza outbreaks to identify the virus strains. In North America, the Centre for Disease Control in United States assembles all information on influenza activity around the world. It then tries to predict the strains that most likely will affect North America and directs vaccine companies to produce influenza vaccine, or flu shot, which can protect all of us during that winter.

The influenza virus is killed and purified during the production of vaccine. As a result, it is not possible to get influenza from the flu shot. Minor side effects include low-grade fever and localized pain. This vaccine is so safe that it is recommended for pregnant women any time during pregnancy, if they have any underlying reason that needs flu shot (e.g. asthma).

The effectiveness of influenza vaccine is about 70%. That is, about 70% of people who receive influenza vaccine can expect themselves not getting sick from influenza. This vaccine is most effective in children and adults who have normal immune system. The vaccine is less effective in elderly people. For those who are not completely protected, the infection is still less severe than those who did not receive the vaccine.

Most people are aware that flu shot is indicated for seniors over 65 years of age. However, very few know that flu shot is also recommended for adults and children with heart or lung conditions that require regular medical care. These include heart disease, asthma, chronic bronchitis, emphysema, etc. Those with diabetes, cancer, kidney disease, blood conditions, metabolic and immune diseases should also get flu shot. Those infected with HIV, the virus that causes AIDS, should be vaccinated too.

Children under 18 who need aspirin regularly (those with arthritis) should get flu shot. If they contract influenza while on aspirin, they can develop a fatal condition of the liver called Reye’s syndrome. Those who live in nursing home or chronic care facilities should also get flu shot, since their environment promotes the spread of influenza virus.

Besides these groups, health care workers should be vaccinated too. It is because these workers are more likely to be in contact with patients in the high-risk groups. If these workers develop influenza, they can spread the deadly virus to these high-risk patients. For the same reason, those who live with patients in the high-risk groups should get flu shot to prevent infection, and passing the virus to these patients. Your family certainly belongs to this category.

There are very few situations where flu shot is not recommended. Influenza vaccine contains a very small amount of egg protein. Those individuals who have anaphylactic reaction to eggs or previous flu shot should not receive this vaccine. Symptoms of anaphylactic reaction include hives, swelling of the mouth and throat, difficulty breathing, low blood pressure, and shock. If you are not sure, check with your doctor.

Flu shot can be given together with other vaccines. This is especially important for senior who may need the Pneumococcal Vaccine that prevents pneumonia. If one has fever due to an infection, flu shot should be delayed until fever is gone. Flu shot can be given to children as young as 6 months of age, below that age the vaccine is not effective.

Lastly, manufacturers of vaccine usually produce more vaccine every year, since the demand for influenza vaccine has been increasing. There should be enough vaccine for everyone who needs or wants one. You should not worry about depriving someone else of this important vaccine if your family gets it.

[Note to Readers: Most of the information in this column is still relevant. There are updated recommendations for influenza vaccine. Please read more recent columns, as well as consulting with your physician, public health nurse, or pharmacist.]