Tweaking flu vaccine for better protection
Flu vaccination in South Africa
“Virology laboratories, including South African laboratories, send 'flu viruses recovered from patients to the WHO reference laboratories. Based on this up-to-date collection, the WHO gives vaccine manufacturers the 'seed stock' of the viruses that should be used to produce the next vaccine. Since 1977 there have been two strains of influenza A circulating around the world, along with the single influenza B strain. Therefore there are three viruses in the 'flu vaccine.
"To increase the accuracy of 'flu vaccines, there are now separate vaccines produced every six months for the winter seasons of the Northern and Southern hemispheres. The vaccine is composed of the current strains of 'flu that are grown in hens' eggs and then chemically inactivated."
Ramped up shots for next US flu season
Having acknowledged that the 2014-2015 flu vaccine was mismatched to the circulating influenza strains, U.S. health officials have ramped up next season's shots for broader protection.
Flu-vaccine makeup is determined months in advance so that manufacturers have time to make the millions of doses needed. Components of the coming "2015-16 season vaccine have been changed to more optimally match circulating viruses," the U.S. Centres for Disease Control and Prevention said in its June 5 Morbidity and Mortality Weekly Report.
There also is a version of the flu vaccine called quadrivalent flu vaccine, designed to protect against four flu viruses; two influenza A viruses and two influenza B viruses.
Last year, no one saw until summer that the H3N2 strain would predominate, said CDC epidemiologist Lynnette Brammer.
Work on the vaccine had begun in February, she said. "[The H3N2 strain] came on so fast, and there wasn't time for it to be included in the vaccine," she explained.
As a result, flu shots were only 18.6 percent effective against the predominant H3N2 strain, she said.
Strains circulating in the United States and around the world
Shots for the coming flu season will contain two influenza type A viruses – H1N1, which caused the 2009 pandemic flu, and last year's virulent H3N2 – plus an influenza B component, according to the CDC researchers.
These are the strains that appear to be circulating in the United States and around the world, and they're expected to be the main strains in the 2015-2016 flu season, Brammer said.
But there are no guarantees, she cautioned.
"Influenza activity is unpredictable in terms of what virus will predominate and the exact timing of the season, and both of these things, along with others, can have a large impact on season severity," she said. "Therefore, we can't know at this point what the next flu season will look like."
Read: Flu and the elderly
As CDC experts looked back on the flu season that just ended, they described it as moderately severe. Hundreds of thousands of people were hospitalised, and thousands died, most of them 65 and older.
"This year was a severe year, particularly for the elderly. Our vaccine match wasn't as good as we would like it to be," Brammer said. "It was an unusual year."
Paediatric deaths on the high side
Deaths from flu ranged from 5 percent to 9.3 percent of all deaths between Jan. 3 and Feb. 21, 2015, the CDC said. That's about average for an H3N2 flu year, Brammer said.
Paediatric deaths were on the high side. The CDC said 141 children died in 40 states. Child deaths usually range from 34 to 171 in a given flu season. The biggest exception was the pandemic 2009-2010 season, when 358 kids died from flu.
The CDC recommends that everyone 6 months and older get a flu shot every year. Brammer said this year's vaccine will be available in September.
"Although we did have a mismatch last season, a flu shot is still the best way to protect against influenza," Brammer said. "We do recommend that come the fall, people should go out and get vaccinated."
When flu vaccines don't work . . .
Global health authorities have cautioned that current flu vaccines may not prevent a severe new strain of influenza, highlighting the need to seek alternative ways to protect against falling ill this winter.
The US Centres for Disease Control and Prevention (CDC) issued a health warning to doctors during the northern hemisphere winter about the severity of the 2015 flu season. It said the current flu vaccination protects against three or four strains but is not a match for the dangerous H3N2 strain which has mutated and has contributed to more deaths and hospitalisations of children and the elderly.
Nearly 30 children died in one of the worst flu outbreaks in the US over their winter. In SA, a new modified vaccine is now available to match two of three new strains, including H3N2. However flu can still be contracted if other strains are not covered by the vaccine.
SOURCES: Lynnette Brammer, epidemiologist, influenza division, U.S. Centers for Disease Control and Prevention; June 5, 2015, Morbidity and Mortality Weekly Report
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