Although this year’s influenza vaccine is not a perfect match for the virus circulating in Canada right now, it is still important for you to get the flu shot.

There are two types of influenza virus that can infect us, A and B. You have heard of the pandemic swine flu (H1N1) virus; it is still around. The most prevalent influenza virus right now is H3N2. Both of them are influenza A viruses. You may also have heard of a recent avian flu (H5N2) outbreak in British Columbia affecting a number of poultry farms.

Influenza A viruses have two proteins, H and N, that scientists can identify. Some can spread very easily from person to person when one sneezes or coughs. The droplets can spread directly to those close by, through handshake, or by touching surfaces where these infectious droplets land. Fortunately avian flu viruses cannot infect us as easily, although they can cause major outbreaks in poultry farms.

All influenza viruses have special ability to share their genes with each other. As a result, the current H3N2 virus is slightly different from the one in the vaccine. The difference is small, but the two viruses are not identical. When scientists met months ago, they scrutinized all the strains of influenza virus around the world, and tried to predict which ones may spread in North America. The decision has to be made months before the launch of influenza vaccine in October each year.

There are usually two strains of influenza A in vaccines. This year, there is one H1N1 (similar to the swine flu virus), and the other is H3N2. Although the H3N2 vaccine virus is slightly different from what is circulating, it doesn’t mean that it is not effective at all. You may still have partial immunity. If you have an infected colleague at work who quickly takes sick leave and stay away, you may be exposed to a small amount of virus only and may not get sick at all. However, if you have a close family member who is sick and spends a lot of time with you, coughing around you, you will get a larger load of virus. The protection that you get from the flu shot may not be able to protect you completely. You may still get sick, although you likely will be less sick than if you never got the flu shot.

Furthermore, in the next few months, other strains of influenza virus may come around, and you will be totally unprotected if you don’t get the vaccine. Since you are looking after your grandmother who has diabetes, you need to protect yourself so that you won’t pass on influenza virus to her. Although she has been vaccinated, her body may not be able to produce as strong an immunity against influenza, and she can still get sick if anyone around her contracts influenza.

Traditionally, influenza vaccines contain two strains of A and one strain of B. This year, some influenza vaccines include 4 strains of influenza virus, two As and two Bs. The hope is that these will provide more protection against influenza B viruses.

In the last few years, a live cold-adapted influenza vaccine has become available and is administered directly into the nose. This live virus can grow in the mucosal cells in the nose, but not in the lungs. Therefore, it cannot cause pneumonia in vaccinated individuals. However, those with weak immune system or those with severe asthma should not receive the live vaccine.

I realize that some people have many reasons for not getting influenza vaccine. Some are suspicious of medical technology and vaccines, and will choose anything natural or homeopathic. Others have heard of friends who got sick after vaccination, or had a winter with more illness after receiving the flu shot. The truth is that influenza vaccine doesn’t make people sick. There can be local pain after flu shot, but not high fever or flu-like illness.

There are many other viruses that can cause colds and flu-like illnesses in winter. We don’t have vaccines to prevent them. When you get flu shot, it will induce immunity against the strains of influenza in the vaccine. It will not make you more susceptible to other virus infections, but it also doesn’t protect you from them either. You can have a winter where you get infected by several different respiratory viruses other than influenza.

Every year, about one-third of us will contract influenza virus, the problem is: we don’t know whether we are part of that one-third. More importantly, we may inadvertently infect those around us who can get very sick or die from it. Outbreaks of influenza in nursing homes are often deadly because many seniors have weak immune system and don’t respond well to the vaccine, and they are very prone to pneumonia. Those with weakened immune system from chemotherapy or other serious illnesses can die from influenza infection. Even if they don’t die, influenza can delay their chemotherapy treatment and alter their ultimate survival.

Although it may sound harsh, we do have responsibility to those around us, whether they are family members, colleagues, or total strangers. We may unknowingly pass on a potentially lethal virus to someone else. When you are young and strong, you may get a bad flu and stay in bed for a week. Someone else may end up in hospital and die from the same virus.

During the pandemic year, most Canadians received the swine flu vaccine, and many stayed home when they were sick. That was the year that influenza caused the least number of school absenteeism or sick leaves. The “herd immunity” reduced the spread of influenza virus. When more people get vaccinated, the virus cannot spread in a community as easily. We all need to do our part to keep everyone healthy.