The 2017-2018 flu season has been one for the record books, and the effectiveness of the flu vaccine prepared for this flu season did not perform as hoped. Because the vaccine did not perform as expected, you might ask why? And, you might ask just how is the vaccine developed in the first place?
According to a report in December by the Center for Disease Control (CDC), the data recorded for the by the influenza surveillance systems using southern hemisphere information from May to September 2017 indicated that the current vaccine was 33 percent effective against all the influenza viruses circulating during the period.
The recommended vaccine prepared for the southern hemisphere contained an A/Michigan/45/2015 (H1N1) pdm09-like virus, an A/Hong Kong/4801/2014 (H3N2)-like virus, and a B/Brisbane/60/2008-like virus. These are the same virus strains used to develop the northern hemisphere vaccine. The data from the southern hemisphere indicated that while the overall effectiveness of the vaccine was 33 percent during the 2017 southern hemisphere flu season, the individual effectiveness specific to the H3N2 viruses was 10 percent.
This individual effectiveness against one of the three strains used to develop the vaccine gave rise to the headlines seen in the media. And, unfortunately, the influenza strain that is causing most of the problems in the United States are influenza A H3N2 strains. Based on a statement from the CDC, the vaccine effectiveness against H3N2 strains is typically lower than those seen for the H1N1 or influenza B strains. And, a common effectiveness for a vaccine against the H3N2 is about 30 percent.
Thus, this year’s flu season has hit the U.S. hard because the predominant type of influenza is one of the more difficult ones to vaccinate against.
But, just how are the influenza strains picked for the next flu season?
Again, according to the CDC, manufacturers projected they would supply the U.S. with 151 million to 166 million doses of injectable vaccine for the 2017-2018 flu season. Which means that the manufacturers had to know ahead of time, before September, which influenza strains MIGHT be prevalent for this year’s flu season. Meaning the manufacturers have to make the vaccine based upon a highly educated guess as to what viruses may be circulating.
The educated guess comes from the World Health Organization (WHO), and the guess for the 2018-2019 flu season was released on February 22, 2018.
The guess comes from gathering data from more than 100 national influenza centers in over 100 countries. These centers collect thousands of influenza samples that come from patients that experienced the flu. The samples are sent to one of five WHO Collaborating Centers for Reference and Research on Influenza. The CDC in Atlanta is one of the centers. The other four are located in London, Melbourne, Tokyo, and Beijing.
Twice per year, in February and September, where the information and data collected is reviewed. From this data, the experts predict as to which strains are likely to be circulating during the next year. For the 2018-2019 season, they have recommended a quadrivalent (meaning containing four different strains) vaccine containing an A/Michigan/45/2015 (H1N1) pdm09-like virus (which was in this year’s), A/Singapore INFIMH-16-0019/2016 (H3N2)-like virus (a different H3N2 strain), a B/Colorado/06/2017-like virus, and a B/Phuket/3073/2013-like virus. According to the WHO, these changes were made because the circulating H3N2 viruses were poorly recognized by the antibodies raised by current A/Hong Kong (H3N2) strain and it is believed that the recommended H3N2 strain would provide better performance. Similarly, the studies have indicated the change of the influenza B strains would also provide better protection against the circulating influenza B strains.
There is a great deal of science that goes into the development of the yearly flu vaccines. Today many of us don’t think about the potentially serious ramifications of a flu outbreak because in recent times we have had access to very good vaccines and medicine.
In 1918, an estimated 50 million people worldwide with about 675,000 in the U.S. died due to flu. The 1957-1958 flu season resulted in an estimated 1.1 million deaths worldwide with 116,000 in the U.S. The 1968 flu season resulted in similar numbers as the 1957-1958 season.
Because of research and advances in tracking and monitoring influenza outbreaks, we have been very fortunate not to have seen numbers like these in quite some time. Thus, while even though the vaccine may not be as effective as hoped, it still does provide some protection. If you need more information about the flu shot, the CDC has distributed answers to frequently asked questions (www.cdc.gov/flu/faq/preventing-flu-illness.htm).
Editor’s note: This is a series of science-related articles by author Frankie Wood-Black, Ph.D., REM, MBA, to appear in Mid-Week section of the Ponca City News. The author currently runs her own environmental consulting firm based in Ponca City, Sophic Pursuits, Inc., and also serves as a Physics Instructor and the Director for Process Technology at Northern Oklahoma College.