Advice for vaccination against seasonal flu

By Yoo Youk-jin

The CDC recommends that all persons aged 6 months and older should get a flu vaccination this year. This represents an expansion of the previous recommendation because healthy nonpregnant female adults aged 18~49 who were not at high risk of influenza infection were not recommended to do so until last year. This is supported by evidence that an annual influenza vaccination is a safe and effective preventive health action with potential benefits for all age groups. Additionally this year’s flu vaccine is designed to protect against 3 different flu viruses: influenza A H3N2, influenza B and the 2009 H1N1 which was previously called ‘swine flu’. Two different flu vaccines will not be necessary like last year.

The first 2 types of influenza viruses are expected to spread this year as seasonal flu viruses. It's likely that the 2009 H1N1 influenza virus will continue to circulate and cause illness this flu season again, like the Spanish flu of 1918 and the Hong Kong flu of 1968 which widely spread for 3~4 years after they first appeared.

You should get vaccinated this year even if you were confirmed with 2009 H1N1 influenza or had the 2009 H1N1 vaccine last year because your immunity weakens. Normally immunity sets in about two weeks after vaccination and provides protection that lasts 6~12 months.

Children 6 months through 8 years of age under the following conditions are recommended to take two doses of this year’s flu vaccine four or more weeks apart to be fully protected;

(1) If the child has not received the seasonal flu vaccine before.

(2) If the child received only one seasonal flu vaccine in 2009 and never before.

(3) If the child did not receive the 2009 H1N1 vaccine in 2009.

In Korea, the first influenza viruses of this year were reported on the 8th of August. One was the 2009 N1H1 influenza virus and the other was the influenza A H3N2 from Gyeonggi and South Gyeongsang Province. The patient with the 2009 N1H1 virus fell ill after visiting New Delhi, India although he had received the vaccination against the 2009 N1H1 virus last November. This is the reason why it is highly recommended to get this year’s flu vaccine and especially since it seems to provide immunity against all of these viruses.

This year’s flu vaccine is available for free at any public healthcare center, if you are in the high risk group of people over 65 years old. The criteria might be different depending on the region, so you should call first.

If you are 19~49 years old without any risk factors or if you are supposed to travel abroad, you can get the 2009 H1N1 monovalent vaccine which can only prevents 2009 H1N1 influenza for free at a public health center.

The author is a clinical instructor at the Seoul National University Hospital International Healthcare Center (SNUH-IHC).