Y S Teo Family Clinic & Surgery

Southern and Northern Hemispheres, in the first instance, refers to the geographical areas of our planet earth.  However, there is a slight wrinkle when we talk about Southern and Northern Hemisphere in reference to influenza vaccines.

The influenza vaccines are designed to be effective for a particular winter season i.e. December 2009 to March 2010 for the coming Northern Hemisphere winter (exact dates as calculated by wolframalpha).  The next Southern Hemisphere winter will be from June to September 2010 (exact dates as calculated by wolframalpha).

Therefore, when we decide to be protected for the upcoming winter season lasting from Dec 09 to Mar 2010 i.e. the Northern Hemisphere winter, we just need to pop down to our nearest friendly family doctor for the shot.  In general, the Clinic will stock the influenza vaccine for the upcoming winter season.

But if I am travelling to Australia which is in the Southern Hemisphere, does it mean I should get the Southern Hemisphere vaccine?  The simple answer is ‘No’.  The reason is that the current upcoming winter is in the Northern Hemisphere.  Therefore, the strains of influenza virii prevalent in Australia would be the same as that in the Northern Hemisphere countries.  For this, we should probably thank the advent of wide-spread and economical air travel.

To generalise, no matter where you are (or are going to travel to) in the world, get the Southern Hemisphere vaccine in the first half of the year.  For the second half of the year, you should get the Northern Hemisphere injection.

People who should get their flu shots

1.  The composition* of the Northern Hemisphere (NH) 2009 winter season influenza vaccine is as follows:

A/Brisbane/59/2007 (H1N1)-like virus

A/Brisbane/10/2007 (H3N2)-like virus

B/Brisbane/60/2008-like virus

This NH 2009 vaccine does not contain the H1N1 pandemic strain.  Thus the need to take both the NH 2009 as well as the H1N1 vaccines.

2.  The Southern Hemisphere (SH) 2010 winter season influenza vaccine contains the following strains*:

A/California/7/2009 (H1N1)-like virus (the pandemic strain)

A/Perth/16/2009 (H3N2)-like virus

B/Brisbane/60/2008-like virus

The recommended H3N2 strain for SH 2010 vaccine (A/Perth/16/2009) is antigenically different from that in the NH 2009 vaccine (A/Brisbane/10/2007).  The relative contribution of the H1N1, H3N2 and B strains to influenza illness in the months ahead cannot be predicted.  Thus, the need for vaccination with the new vaccine available in Feb/Mar 2010 once it is available  —> because the strain of H3N2 protected against, in the Feb/Mar 2010 vaccine will be different.

* The composition of the influenza vaccines is determined by a panel of WHO experts.  This WHO panel of experts sits every 6 months to predict the likely prevalent strains of influenza virii causing illness in the forthcoming winter based on their expert opinion.