Why the Flu Vaccine Barely Worked This Year

Published: Apr 08, 2015

Why the Flu Vaccine Barely Worked This Year
April 1, 2015
By Renee Morad, BioSpace.com Breaking News Staff

If you got the flu vaccine and still got the flu this year, you were certainly not alone.

This year’s influenza vaccine was just 18 percent effective against the dominant H3N2 strain of the flu in circulation, according to the U.S. Centers for Disease Control and Prevention (CDC) . This is down from previous estimates that the vaccine was 23 percent effective.

The injected vaccine for children between the ages of two and eight was even worse, at just 15 percent effective, and the nasal-spray version may not protect young children at all, according to the CDC.

The flu vaccine market showed signs of growth at the onset of this year’s flu season, when companies expected to ship about 160 million doses of the vaccine for the U.S. market, compared to nearly 135 million doses produced last season, according to the CDC. Sanofi Pasteur, the largest distributor of the flu vaccine in the U.S. and maker of Fluzone, announced plans to supply at least 65 million doses this season. Novartis planned to ship 30 million doses of two flu vaccines – Flucelvax and Fluvirin. GlaxoSmithKline planned to ship around 28 million doses. Other makers, such as MedImmune, maker of FluMist, planned to ship between 14 million and 15 million doses, while Protein Sciences, maker of recombinant egg-free vaccine Flublok, planned to supply around 500,000 doses.

Despite the growing supply, the vaccine fell short when it came down to protecting against this year’s dominant strain. The vaccine’s 18 percent effectiveness was the lowest the agency has seen since it began tracking effectiveness in 2004-2005, when the effectiveness was at 10 percent. Since then, effectiveness rates have fluctuated between 20 to 60 percent, with the strongest year (60 percent) occurring in 2010-2011. Last year, the vaccine was 51 percent effective.

“These numbers, which are lower than we normally see, are because the flu viruses that are circulating have mutated to look very different than the vaccine strains,” said Joseph Bresee, chief of the Epidemiology and Prevention Branch at CDC’s National Center for Immunization and Respiratory Diseases.

The H3N2 flu strain wasn’t factored into this season’s vaccine, which takes about four months to make. The strain was seen for the first time in March 2014, while the World Health Organization’s (WHO) procedures and decisions regarding which strains to include in the vaccine were made a month earlier in February. The decision is finalized before the beginning of the next year’s flu season to account for production and distribution time.

In fact, an FDA advisory committee just recently endorsed the WHO’s choice of influenza strains for the 2015-16 seasonal flu vaccine. The WHO recommended changing two of the three strains in trivalent flu vaccines for the next Northern Hemisphere flu season: H3N2 and influenza B. The FDA’s Vaccines and Related Biological Products Advisory Committee unanimously approved the WHO’s H3N2 selection, which was widely expected since most of the circulating H3N2 viruses in the U.S. and a number of other countries did not match well with the vaccine this year.

The flu strain selection process for the vaccine gets a bit more complicated when considering that each year new strains can emerge and mutate and are therefore unpredictable. Unlike the measles vaccine, which is relatively straightforward since there is only one antigenic type of measles virus, there are hundreds of different strains of influenza to mull over when trying to create a vaccine.

“Once vaccine production commences, it is not possible to change the chosen vaccine strains if a drift is detected,” Polina Miklush, a spokesperson for Novartis, said in an emailed statement to BioSpace.

Novartis, which could not comment on the WHO’s procedures and decisions regarding which flu strains to choose in the vaccine, is “committed to addressing unmet needs in influenza prevention and working closely with local government bodies to protect those most at-risk,” Miklush said.

Meanwhile, the public is questioning the necessity of the flu vaccine more than ever before. In this year’s early flu season (November 2014), 42 percent of children and nearly 40 percent of adults were vaccinated. In comparison, 51 percent of children and 40.5 percent of adults were vaccinated in 2010.

For some people, the potential side effects of the flu vaccine are enough to deter them. Ann-Marie Piscitelli, of North Haven, Conn., said she stopped getting the flu shot several years ago when she came down with the virus five days after receiving the vaccine.

Others, like Joe Latham, of Middlefied, Conn., would rather roll the dice than “get a small dose of year’s expected strain of the flu.” He explains, “I’m not a fan of giving my body something that it may not even come in contact with.”

The CDC recommends that everyone aged 6 months and older get vaccinated. In addition, the agency suggests taking precautions such as early treatment with antiviral drugs such as Tamiflu and Relenza, along with washing hands frequently and covering your mouth when coughing and sneezing.

Meanwhile, scientists are fast at work trying to devise a strategy for a more effective vaccine. They are looking for antigens that correspond to the parts of the virus that stay the same, even when the rest of the virus has changed. An influenza vaccine developed by scientists at Okairos, a company based in Rome, Italy that is pioneering the development of T-cell based vaccines for infectious diseases, for example, was tested at the FDA and shows potential as a “universal” vaccine to protect against a broad range of flu viruses.

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