The 2014-2015 flu season is drawing to a close, and looking back, there is no doubt – it was a bad year. While millions of people were quick to get a flu shot, many of them ended up getting the flu nonetheless. According to CDC data, this year’s flu vaccine was only 18 percent effective! In addition, flu related hospitalizations for people aged 65 and older were at the highest rate in at least a decade. With all the global cooperative work that goes into the development of the flu vaccine, what could have gone wrong?
Well, let’s step back a moment, and try to understand how the flu operates every year. While the flu season in North America generally lasts from mid-fall to late winter, the viral strains are monitored year-round. We know that it is inevitable, but careful research can minimize the yearly public health crisis that is the flu season.
The flu is not a disease like polio or smallpox, where a one-time vaccination will keep you safe for life. The flu virus is constantly mutating, and the flu shot can only protect you from particular strains that will change the following year. Each year, researchers from over 100 countries use long-term epidemiologic trends to monitor which strains are the most active, and therefore, should go into the vaccine. This data is then sent to the World Health Organization (WHO), then the development of the vaccine begins. Dr. Steven Lawrence, an infectious disease specialist and assistant professor at the Washington University School of Medicine, says that the prediction of which flu strain will circulate is very meticulously calculated, but is still prone to error, in part because of how early that prediction must be made. “The technology that is used to produce over 90 percent of the flu vaccine used in the world is based on growing flu viruses in chicken eggs” Lawrence remarked, noting that this creates a time constraint on the strain-predicting process, “[Growing the vaccine] requires millions of chickens, and millions of eggs, and the whole process takes about six months to make enough flu vaccine for the whole country, so you have to start the process well in advance.”
The viral strains are classified into influenza A and B, and influenza A is further subdivided into H1N1 and H3N2 strains. Every year, the flu vaccine contains three or four viral strains, containing at least one H1N1 strain, one H3N2 strain, and one influenza B strain. Lawrence says that as of March 2015, the flu strains for the 2015-2016 flu season have likely already been predicted, and the vaccine has begun development based on those predictions.
However, there are hundreds of strains to select from! And therein lies the problem – making the right prediction so early on. According to Lawrence, there is little room for mistakes. “If you don’t have a near perfect match, you don’t get a great immune response that will fully protect you,” commented Lawrence, adding that the vaccine can still provide “partial protection.” Usually, the vaccine ends up being 50-60 percent effective. But every three or four years, there is a mismatch between the vaccine strains and the circulating strain. And this year, the WHO predicted the incorrect form of the H3N2 virus.
The Washington University in St. Louis (WUSTL) campus felt the effects of the vaccine mismatch anomaly. Dr. Lisa Ross, WUSTL’s Director of Clinical Services, says that the abnormally harmful flu season has, while not to a major degree, been evident at the school. According to Ross, every year, Student Health Services at WUSTL orders a shipment of flu shots well in advance, and hopes that they don’t run out. The last flu season at WUSTL that was particularly harsh was in 2009 – the swine flu season. In 2009, additional flu shots needed to be ordered midway through the season, and when Student Health Services at WUSTL (SHS) discovered they were running low on Tamiflu, a medicine used to treat the flu, they found themselves having to ration the treatment based on severity of illness. Ross says that the illness typically picks up on campus after winter break. “People are exposed to people from all different places, they come back and bring all their new influenza germs,” Ross explained. Other factors include activities such as sorority recruitment, where students spend a lot of time in close proximity with each other and compromise their immune system through drinking and lack of sleep.
So what can we learn from this year for the future? Dr. Lawrence is optimistic about the future of flu research. Lawrence says that while the flu will likely never be eradicated, improvements in technology and surveillance have led to more protective vaccines over the years, and will continue to improve over time. According to Lawrence, the ultimate goals are to bring flu shot effectiveness up from 70 percent to 90-100 percent, to reduce the frequency of vaccine mismatches from once every three or four years to once every decade or so, and to develop a flu shot that provides enough protection such that a new one is not needed every single year. “I think it is pretty likely that in our lifetimes … we will have flu vaccines that will provide much broader and longer protection, and we won’t require annual vaccines,” said Lawrence. Moreover, Lawrence remarks, while we can’t stop the flu from mutating, we very well can prevent it from becoming such a large-scale public health threat every year as it is now.
Meanwhile, on the individual scale, the usual recommendations from SHS remain; wash hands frequently, stay away from others who have caught an illness, and if you catch the flu, isolate yourself, or wear a mask if necessary. Dr. Ross confirms that students should “absolutely” continue to get their flu vaccinations, and emphasizes that while the shot will never be 100 percent effective, the figure is usually around 60 percent. And even this year, when it is at 18 percent, there is little reason to not get vaccinated. Even if the shot were only 1 percent effective, you would be 1 percent safer.