Good article on the Flu for 2016-2017 year: https://www.cdc.gov/flu/pdf/freeresources/general/factsheet-whats-new-2016-17.pdf
I (or a friend or family member) received the flu shot this year, but still tested positive for a Type A influenza - what's the deal?
This year's influenza vaccine (2016-2017) vaccinated against Type A: H1N1 California, H3N2 Hong Kong),and Type B - Brisbane. This is a 'trivalent' vaccine. If you received your vaccine at Bridgestone, this is the variety you received. If you happen to be over 65 years old (and still working at Bridgestone PSR/LTR, for which we thank you), you may have received a adjuvent version from your doctor's office or local pharmacy which is designed to create a stronger immune response.
Vaccine effectiveness, however, can vary based on the type you were vaccinated against, versus the actual virus type or sub-type you were exposed to. The H3N2 Hong Kong virus has been found to evolve quickly according to studies between 2004-2015.
Eh? How is that possible?
Virus evolve, that's what they do to survive. So adaptation isn't really surprising. The other two types of viruses in the vaccine don't evolve as quickly. However, the H3N2 evolves very quickly. Most flu vaccines are developed in eggs. There are two other methods, but more on that later. The CDC and WHO provide manufacturers with viruses (the most virulent strains of the previous year) which are grown in eggs per FDA requirements. They are then injected into hen's eggs and incubated for several days to allow the viruses to replicate. Fluid from the egg is then harvested, inactivated (killed), then purified. These are given as vaccines.
During the months between the time the vaccine that is recommended, delivered to the manufacturer, produced, and distributed, the original virus appears to be evolving. This is primarily occurring very quickly with the H3N2 strain. Depending on which strain or sub-strain of the evolved strain you are exposed to, you may have a perfect match with effective coverage, or an imperfect match with limited, or no coverage. So if you have flu symptoms and are tested for the flu virus, you may find that you do indeed have a Type A influenza, even though you were vaccinated against it.
How will I know what happened? Why bother with the flu shot?
The flu vaccine is designed for the most virulent strains, two of A and one of B. There is also a C strain which is causes milder symptoms, so people are not vaccinated against it. If you are exposed to an influenza virus (by vaccine or infection), your immune system makes antibodies against the antigens of the virus. This allows the anti-bodies of your body to attach to the virus and inactivate it (think of velcro on a micro-scale).
The CDC studies about 2000 strains of influenza virus to see (a) how similar they are to the strains included in the current flu vaccine, and (b) how easily the body will develop an immune response to the circulating viruses. That is, how effectively the anti-bodies bind to and inactivate the virus. If antibodies are antigenically resemble a different but similar influenza virus, it will produce an immune response against the circulating virus. They also monitor changes in the circulating viruses to see how the virus changes. This is how viruses are selected for the next season's vaccine.
Ironically, you will not be able to predict which strain or sub-strain of the flu you are likely to be exposed to. We know that the vaccine protects against H1N1 and Brisbane. Depending on which evolution of the H3N2 strain you are exposed to, you may have excellent coverage, or none.
I do recommend getting the vaccine early in the season. If you are exposed to the flu, you have protection and will develop immunity to that particular strain and it's kin, which should afford protection to it's evolutionary form coming around a couple weeks later. Meaning, mild or no symptoms. Conversely, if you are exposed to a later strain that evolved after your vaccination, you may not have effective protection.
This year's influenza vaccine (2016-2017) vaccinated against Type A: H1N1 California, H3N2 Hong Kong),and Type B - Brisbane. This is a 'trivalent' vaccine. If you received your vaccine at Bridgestone, this is the variety you received. If you happen to be over 65 years old (and still working at Bridgestone PSR/LTR, for which we thank you), you may have received a adjuvent version from your doctor's office or local pharmacy which is designed to create a stronger immune response.
Vaccine effectiveness, however, can vary based on the type you were vaccinated against, versus the actual virus type or sub-type you were exposed to. The H3N2 Hong Kong virus has been found to evolve quickly according to studies between 2004-2015.
Eh? How is that possible?
Virus evolve, that's what they do to survive. So adaptation isn't really surprising. The other two types of viruses in the vaccine don't evolve as quickly. However, the H3N2 evolves very quickly. Most flu vaccines are developed in eggs. There are two other methods, but more on that later. The CDC and WHO provide manufacturers with viruses (the most virulent strains of the previous year) which are grown in eggs per FDA requirements. They are then injected into hen's eggs and incubated for several days to allow the viruses to replicate. Fluid from the egg is then harvested, inactivated (killed), then purified. These are given as vaccines.
During the months between the time the vaccine that is recommended, delivered to the manufacturer, produced, and distributed, the original virus appears to be evolving. This is primarily occurring very quickly with the H3N2 strain. Depending on which strain or sub-strain of the evolved strain you are exposed to, you may have a perfect match with effective coverage, or an imperfect match with limited, or no coverage. So if you have flu symptoms and are tested for the flu virus, you may find that you do indeed have a Type A influenza, even though you were vaccinated against it.
How will I know what happened? Why bother with the flu shot?
The flu vaccine is designed for the most virulent strains, two of A and one of B. There is also a C strain which is causes milder symptoms, so people are not vaccinated against it. If you are exposed to an influenza virus (by vaccine or infection), your immune system makes antibodies against the antigens of the virus. This allows the anti-bodies of your body to attach to the virus and inactivate it (think of velcro on a micro-scale).
The CDC studies about 2000 strains of influenza virus to see (a) how similar they are to the strains included in the current flu vaccine, and (b) how easily the body will develop an immune response to the circulating viruses. That is, how effectively the anti-bodies bind to and inactivate the virus. If antibodies are antigenically resemble a different but similar influenza virus, it will produce an immune response against the circulating virus. They also monitor changes in the circulating viruses to see how the virus changes. This is how viruses are selected for the next season's vaccine.
Ironically, you will not be able to predict which strain or sub-strain of the flu you are likely to be exposed to. We know that the vaccine protects against H1N1 and Brisbane. Depending on which evolution of the H3N2 strain you are exposed to, you may have excellent coverage, or none.
I do recommend getting the vaccine early in the season. If you are exposed to the flu, you have protection and will develop immunity to that particular strain and it's kin, which should afford protection to it's evolutionary form coming around a couple weeks later. Meaning, mild or no symptoms. Conversely, if you are exposed to a later strain that evolved after your vaccination, you may not have effective protection.
