Influenza Vaccine

The influenza vaccine is the most effective way to prevent influenza (including swine flu) and is taken annually.

Why annually? – because the viruses that cause influenza are continuously mutating and the vaccine is only effective

against the strains that compose the vaccines and the related strains. It is ineffective against unrelated strains and therefore it is vital that the vaccine covers the currently prevalent strains.

Who should get the flu vaccine?

All individuals > six months of age must receive the flu vaccine. Infants who are less than six months of age cannot mount the appropriate response to the vaccine. Therefore, it is recommended that all caregivers in contact with infants less than six months of age must definitely take the vaccine.

Are multiple doses required?

Since the strains that cause influenza illness vary every year, flu vaccine needs to be repeated every year. In children who are < 9 years of age, a second dose of vaccine, at least one month apart, should be given in their first flu season to optimize their immune response. The latest recommendation (2012) is that even if it is the child’s second season and he has received only one dose in the previous season, he should be given two doses in the second season.

When should the flu vaccine be administered?

It should preferably be given before the onset of influenza activity and if not possible, as early as possible at the start of the flu season. In India, the flu season is biphasic – one peak is in the monsoon months and one around January & February though it can occur any time of the year in tropical regions like India. If a person has not been vaccinated in that year, then the vaccine can be given at any time.

How effective is the vaccine?

Firstly it takes two weeks for the immunity to come through. Overall 50% – 80% of individuals who receive the vaccine will be protected against the illness.

Can I avoid taking a shot? Is there any other way to immunize myself?

The flu vaccine is available in two forms – the injection and the nasal spray. Injection is approved for individuals more than 6 months of age and the nasal spray for healthy children who are more than 2 years of age and in healthy adults who are less than 49 years of age. However for the 2016-17 season, nasal spray route for administering the vaccine is not recommended. Effectively this year, we only have the injectable route available. From May 2011, a third route, the intradermal route has become available and is recommended for individuals between 18 and 64 years of age.

In fact now the CDC prefers the nasal spray over the flu shot in ‘healthy’ children who are between two and eight years of age when available. If not available, one should not delay immunization but give the injectable form.

Why is there a emphasis on healthy individuals who receive nasal spray?

The nasal spray has live viruses that have been weakened in the labs. If a person is sick or in case of pregnant females, his / her immune system is weakened and the person may not be able to defend himself / herself even against the weakened virus and may actually develop flu.

Are there any side-effects of the vaccine?

Yes, minor side-effects like soreness at the injection site, body-aches, low-grade fever (<38° C) and headache may occur and may last for a day or two. There are potentially major side-effects but these are extremely rare.

Allergy to the vaccine

You must inform the doctor if you are allergic to eggs or egg products because the viruses have been grown in eggs and may cause a serious reaction in people who have egg allergy. If you have had hives only as part of egg allergy, the inactivated (injectable) vaccine should be given rather than the spray route, but this should be given by a doctor well-versed and equipped to handle allergic reactions, and that you are under observation for at least 30 minutes after the vaccination. If the reaction to eggs has been more severe than hives, influenza vaccination should be avoided.

Are there no medicines that can be given to prevent influenza apart from the flu vaccine?

There are anti-viral medications that can be given to people who have been exposed to the virus and have not yet been vaccinated. They are also given to the high-risk groups who for some reason cannot be vaccinated. There are significant side-effects to the drugs used, and makes this method undesirable for others.

Pregnant Women

All pregnant women must receive influenza vaccine and can be given any time in any trimester of pregnancy. The risk of complications and hospitalization is 4 times the normal in pregnancy and this risk increases further along the pregnancy is. The vaccine not only protects the mother but the protection extends to the baby up to the age of six months by transfer of antibodies.

If it is not fully effective, why should I give it to my child?

Vaccine efficacy varies every year. This efficacy is measured by how many cases of influenza it prevented. The problem is that the influenza virus undergoes mutation all the time. The vaccine is made up of the viral sub-types that were most prevalent last year. There is no guarantee that the same sub-types will be around this year too, explaining its less than complete efficacy. Last year (2015-16), it was 60% effective.

So why give the vaccine?

Prevents or reduces the severity of the illness

Influenza is a bad illness and in rare cases can result in death too. In others, it makes you significantly sick and you feel miserable and weak for days on end. Even if not 100% effective in preventing influenza, it decreases the severity of the breakthrough infection.

Protects others who cannot take the vaccine

Babies less than 6 months, children who are receiving drugs like steroids or anti-cancer drugs cannot be given the influenza vaccine. They have a double whammy, because their condition predisposes them to easily fall sick with influenza vaccine should they come in contact with the influenza virus.
If others, adults or children, are fully vaccinated, then they are less likely to fall sick with influenza. The umbrella of protection of the influenza vaccine is extended on to this vulnerable population too. What better way of being socially responsible?