Back in November of 2012, it was a year of both an early and severe flu season in the United States but the news coming out of the Centers for Disease Control and Prevention or CDC in Atlanta was encouraging. It said that 90 percent of influenza viruses which were being seen that season were well-suited to the 2012–2013 flu vaccine. That meant that the vaccine that had been given that year should have offered very good protection.
However the effectiveness of the influenza vaccine that season against H3N2, which was the foremost flu strain going around, only ended up to be 46 percent in individuals in ages 18 to 49, 50 percent in people who were in the age range of 50 to 64, and it performed miserably at under 11 percent in people who were age 65 and older, probably one of the most defenseless groups. Influenza hospitalizations and deaths were among the highest see in nearly a decade. What had went wrong?
Research has shown that the H3N2 vaccine strain chosen by the World Health Organization or WHO, was indeed matched up to the flu viruses that were going around at that time. However the strain sent to the makers of the vaccine, which is first modified to grow in chicken eggs which are then used to create the actual vaccine, ended up being incompatible and was ended up being poorly effective, they found.
The most likely reason for the failure of the vaccine say the scientists, is due to three mutations that were inside the egg amended strain which were not found in the WHO strain. This resulted in deviations at crucial sites of the haemagglutinin surface protein which is known to upset the antibody reactions.
Moreover, the researchers discovered the identical problem most likely arose with a different H3N2 element of the 2013–2014 flu vaccine. Every season’s vaccine is supposed to also ward off H1N1 and influenza B type viruses. This means that the possible effectiveness against H3N2 could be considered poor in those seasons’ vaccines as well.
Influenza viruses are always changing, and so the seasonal flu vaccines have to changed year to year in order to improve the circulating vaccine strains. If there is any type of drop in efficiency that takes place in the circulating strains, then there is a process in which mutations end up accumulate in the genes and encode flu antigens which are no longer recognized by the immune system.
Yet the new discoveries have shown that it is vital to make sure the egg adapted virus is well matched, and also to have a better understanding of how specific mutations affect the effectiveness of vaccines.
H3N2 viruses have been shown not to grow very well inside eggs, so in order to formulate the vaccine, the WHO strain has been mixed up with strains that do. The faster growing vaccine strains are used for production. But there has always been the worry about egg mutations causing an alteration of the vaccine.
Efforts are going to start being made to monitor for such mutations and watch for changes. Quality control of the various strains is done by WHO. The organization briefly acknowledged the problem in February of 2013 when it mentioned that the H3N2 strain that was used in the 2012–2013 season should not have been used again in the 2013–2014 season but needed to be replaced with a different strain. WHO has suggested that a completely new vaccine strain be used in the 2014–2015 season and that the findings show that changing vaccine production from eggs to a modern production system which uses human cells.
All in all flu vaccinations remain the best way to guard against flu, but its general effectiveness is poor when equated to vaccines for other illnesses. Back in November of 2012, it was a year of both an early and severe flu season in the United States. However the news coming out of the Centers for Disease Control and Prevention or CDC in Atlanta was encouraging. It said that 90 percent of influenza viruses which were being seen that season were well-suited to the 2012–2013 flu vaccine. That meant that the vaccine that had been given that year should have offered very good protection. However it would soon show they were wrong in their findings.
By Kimberly Ruble