The Dominant H3N2

For those who don’t know: hens will lay eggs regardless of whether a rooster gives her company or not. A hen’s body is naturally built to produce an egg in a day.

Vaccine manufacturers grow a lot of flu viruses in order to produce flu shots, and since the virus grows effectively in eggs, it’s injected into the fertilized hen’s eggs and incubated for days while they replicate; they’re then harvested from the eggs, killed or inactivated, and purified to go into vaccines.  

It’s the season of flu in North America. Since anyone in the vicinity of the infected can fall sick, avoid, if possible, a visit to the hospital where there’s a flood of patients with flu because you might return home with a sore throat, the first of the signs. Although we took flu shots late last year, it’s only 25 to 35% effective. Because whenever a dominant strain like the H3N2 virus circulates, the vaccine offers weak protection.

Image courtesy: CDC

Two malefactor species of influenza A and B viruses cause seasonal flu.  Every year, public health agencies throw an educated guess as to which strains of these species will circulate in the next season. The US Food and Drug Administration approves vaccines that could treat the predicted strains based on laboratory and clinical studies; an error here could undo the vaccine’s effectiveness.

But it’s tough to vaccinate against H3N2, a strain of influenza A. This virus, unlike other viruses, can power-mutate as it spreads through crowds at a breathtaking rate. Though there are modern cell-based and recombinant methods of vaccine production, it isn’t clear whether they or the egg-based vaccines are more protective. Growing the flu virus in eggs is cheap and efficient, but the egg-based approach in relation to H3N2 has so far been ineffective, for the virus mutates to adapt to the eggs, resulting in a vaccine mismatch.

Warning: It’s Flu Season.