How Vaccines Affect the Spread of Influenza…
Early flu season estimates of seasonal influenza vaccination in the United States have indicated that as of early November 2013, more than 60% of Americans, both adults and children, had not yet received a flu vaccination and could be at risk of flu infection and complications. Later, between the weeks ending December 21st and 28th, 2013, widespread seasonal flu reports to the CDC soared from just 10 up to 25 states reporting. According to these reports, at least half of the geographic regions within the state reported flu activity.
Annual vaccination for everyone 6 months of age and older is recommended by the CDC as the best way to protect against the flu1. However, the flu season can be unpredictable and can vary every year because the flu virus is constantly changing. Small changes can occur in viral genes, known as antigenic drift, or major changes may occur, known as antigenic shift. We will learn more about antigenic shift in our next series, when we discuss the emergence of a new influenza virus strain to which the human population has never been exposed. This type of strain is known as a pandemic flu, and it may occur as a result of antigenic shift.
Now let’s learn why antigenic drift causes flu strains to change every year. The annual flu vaccine contains three to four flu strains. In influenza vaccine research after vaccination, the body produces antibodies against these strains, and if a person is exposed to the flu virus, the body’s antibodies will bind onto the viral hemagglutinin (HA) antigens to prevent the infection. To fight back, the virus makes small changes in the HA genes. These changes result in an adjustment in the HA antigen shape so that it can no longer bind to the body’s antibodies, allowing the infection to occur.
On a population-wide scale, these small changes result in viral antigenic drift. This drift is why a different flu vaccine is required every year. To predict which strains to include in the vaccine each year, over one hundred national influenza centers around the world send viral samples to the World Health Organization (WHO). The WHO makes recommendations, and then each country makes a final decision on the specific strains to include. However, there is always a possibility of a less than optimal match of seasonal strains and the current vaccine, which illustrates the importance of development of a cross-protective, or universal, vaccine.
WCCT Global recognizes the importance of Influenza vaccine research and development. To aid pharmaceutical and biotech companies in vaccine development, WCCT Global is equipped with a specialized clinical research unit for vaccine clinical trials, equipped with 30 individual private rooms, separate HVAC systems for controlled ventilation, and separate dedicated units for virus and vaccine storage. If you would like more information about how WCCT Global can assist your organization with your next vaccine clinical trial, CLICK HERE