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How Flu Strains are Selected for the Seasonal Flu Vaccine Each Year

March 14, 2018 6 comments
SereseMarotta_FamiliesFightingFlu-300x300by Serese Marotta, Chief Operating Officer of Families Fighting Flu 

 

The Centers for Disease Control and Prevention (CDC) recommends that everyone ages 6 months and older, with rare exception, get an annual flu vaccine. But did you ever wonder how the flu strains are selected for the seasonal vaccine every year?

A lot more goes into the decision than you might think!

Seasonal flu vaccines contain three (trivalent) or four (quadrivalent) flu strains. Because flu is a complex, dynamic virus that is constantly changing, there are more than 100 monitoring centers in over 100 countries located across the globe that monitor flu activity on a year-round basis to identify which flu strains are circulating.

These centers receive and test thousands of influenza virus samples from patients. They then send representative virus samples to five World Health Organization (WHO) Collaborating Centers for Reference and Research on Influenza, located in Atlanta, GA (i.e., the CDC); London, United Kingdom; Melbourne, Australia; Tokyo, Japan; and Beijing, China. The surveillance data gathered from these samples, along with other information, are used to make a recommendation on which flu strains should be included in the upcoming year’s seasonal flu vaccine.

Contrary to popular belief, the flu vaccine is not just based on last year’s flu viruses. Three general sources of information are considered in the selection of flu strains for the seasonal flu vaccine:

 

  • Surveillance data represents information gathered from the influenza monitoring centers that collect virus samples from patients. Experts use this information to determine which flu strains are circulating and where.
  • Laboratory data refers to antigenic characterization of the flu viruses in a laboratory, which simply means the identification of specific molecular structures on the influenza virus that are recognized by our immune systems and elicit an immune response. The antigen is the “invader” (i.e., in this case, the flu virus) that causes our immune systems to launch an attack through the formation of specific antibodies. Antibodies are what our bodies produce following flu vaccination so that it’s properly “armed and ready” to recognize and fight that specific flu virus if and when we’re exposed.
  • Genetic characterization of flu viruses may also be considered in the selection of vaccine strains. This refers to “mapping” of the genetic codes that make up each flu strain, which allows the experts to monitor changes in circulating flu viruses.
  • Data from clinical studies on vaccine effectiveness are also considered.

With this robust amount of data in hand,  the WHO then meets twice per year to make a recommendation for flu vaccine strains for the upcoming season: once in February to recommend flu strains for the Northern Hemisphere seasonal flu vaccine, and again in September to recommend flu strains for the Southern Hemisphere seasonal flu vaccine. But it doesn’t stop there! Each country then considers the WHO recommendation, reviews the available information, and makes their own decision on which flu strains to include in their country’s seasonal flu vaccine.

In the U.S., once the WHO makes their recommendation for flu strains for the upcoming year’s seasonal flu vaccine, an advisory committee from the U.S. Food and Drug Administration (FDA) meets in February or March to review the WHO’s recommendation and supporting information and vote on the final selection of flu strains. The role of the FDA is an important one, because once the flu strains are selected, the FDA produces materials in their laboratories that are critical for actually producing the flu vaccines. For instance, the FDA provides vaccine manufacturers with the seed viruses and the potency reagents needed to ensure that flu vaccines made by one manufacturer are similar to those made by another. The FDA also conducts quality control measures by ensuring that batches (referred to as “lots”) of flu vaccines released by the manufacturers meet appropriate standards and reflect the correct genetic composition.

Following the selection of flu strains for the seasonal vaccine and receipt of the appropriate materials and information from the FDA, private sector manufacturers begin the process of making the vaccines. All flu vaccines in the U.S. contain the same flu strains, i.e., the flu vaccine available in New York contains the same three or four flu strains as the vaccine that’s available in California. And it’s important to remember that all flu strains (influenza A or B) can be potentially dangerous, regardless of an individual’s health status, and are capable of causing serious illness, hospitalization, or even death.

Influenza is a vaccine-preventable disease that has the ability to affect all of us around the world, which is why it remains such a pressing global public health issue. Seasonal flu vaccines may not be perfect, but given the complexity of flu viruses and their ability to change and mutate frequently, the U.S. does have a solid, scientifically-based approach for flu vaccine development. While much research and development is being done for a universal flu vaccine, the possibility of this technological advancement is still many years off.  In the meantime, let’s not forget all the hard work and research that goes into helping to protect us with the currently available seasonal flu vaccines. And if you’re wondering “why bother” with a flu vaccine that may be substantially less than 100% effective, let’s remember that something is better than nothing, especially when it comes to your life or the life of a loved one.

More in-depth information on how flu strains are selected for the seasonal flu vaccine every year are available from the CDC and FDA


FFF logo_R copyAbout Families Fighting Flu:  Families Fighting Flu (FFF) is a national, nonprofit, 501(c)(3) volunteer-based advocacy organization dedicated to protecting the lives of children and families by helping to increase annual influenza vaccination rates, especially among children 6 months and older and their families.  Our members include families whose children have suffered serious medical complications or died from influenza, as well as healthcare practitioners and advocates committed to flu prevention.  In honor of our children, we work to increase awareness about the seriousness of influenza and to reduce the number of hospitalizations and deaths caused by the flu each year.

Worldwide Ban on Thimerosal Would Cost Lives

December 17, 2012 149 comments
Amy Pisani, Executive Director of Every Child By Two, offers insight on an important global decision regarding thimerosal in vaccines. 
 

Today, the American Academy of Pediatrics is supporting the World Health Organization’s position to continue to use the preservative thimerosal to vaccinate children in developing nations.

As our readers are most likely aware, thimerosal was removed from the majority of vaccines provided to infants and children in the U.S. due to concerns that this mercury-based preservative could cause detrimental effects.  So why would the World Health Organization (WHO) and the American Academy of Pediatrics (AAP) support the continued use of thimerosal in foreign countries?  The simple answer is that thimerosal is a safe and necessary component of vaccines and that millions of lives would be lost if efforts to ban it globally were to succeed.  But the story behind the decision is not as simple.

Thimerosal…what is it, and how did that one word spread havoc in the hearts of a nation at the outset of the new millennium?

Thimerosal is an ethyl mercury based preservative that prevents the growth of bacteria and fungi.  The preservative was included in all multi-dose vials of vaccines to eliminate the chances of contamination, which could occur as syringe needles are reinserted into multi-dose vials.  This contamination has the potential to cause severe reactions at the site of the injections, as well as serious illness and even death, hence the need for a stable preservative in the vials.

PD_0173Up until the late 1990s many of the vaccines used in the U.S were in multi-dose vials and therefore included thimerosal.  The Food and Drug Modernization Act of 1997 required that the Food and Drug Administration (FDA) review mercury content in all biological products.  The review noted that the cumulative amounts of ethyl mercury found in the vaccine series given to young infants could potentially exceed the US Environmental Protection Agency (EPA) guidelines.   It is important to note that the EPA’s standards were stricter than those of the FDA or the Agency for Toxic Substances Disease Registry (TSDR).  Vaccines did not surpass the levels set forth by either the FDA or TSDR.

In response to the EPA findings, the AAP and US Public Health Service (USPHS) called for the elimination of mercury in vaccines as a precautionary measure.  Manufacturers responded by altering production procedures to create single dose vials of those vaccines that were formerly stored in multi-dose vials.  The only vaccine for children that currently contains thimerosal are some doses of influenza vaccination – a necessary decision due to the need to rapidly disseminate vaccines, particularly in face of serious pandemics of influenza.  Most people are unaware that several vaccines, including MMR (measles, mumps, rubella) vaccine, never contained thimerosal in the first place.

As it turns out, the EPA standards were set for methyl mercury, commonly found in fish and wildlife, which are themselves contaminated through environmental mercury pollution.  Methyl mercury, which accumulates in the body at least seven times longer than ethyl mercury, has been proven to cause adverse neurodevelopmental effects.

What we have learned.

In the time since the decision was made to remove thimerosal from vaccines, numerous studies have been conducted worldwide to determine the effects of thimerosal on infants and children.  These studies have found no evidence that the preservative causes harm to infants or children.  Special attention has been focused on the question of whether the removal of thimerosal from vaccines would result in a rapid decline in autism cases.  This was not the case; even with the decline in use of thimerosal containing vaccines, autism rates continued to climb.

It was hoped that by clarifying the difference between methyl and ethyl-mercury, the lack of that one letter “m” in front of the word describing a dangerous compound, the fears of a nation would be alleviated…no such luck! Read more…