Influenza season is upon us. Traditionally from October to May is the time of year when various strains of influenza virus start circulating in earnest in the U.S.
Immunization against influenza can help prevent children and adults from contracting the disease.
However, there are big changes in this season’s recommendations.
The two main types of influenza virus are influenza A and influenza B. Both consist of multiple strains of influenza virus.
The viruses tend to mutate readily and combine freely with strains from certain animals (swine and birds, for instance).
This is why the influenza vaccine usually differs from year to year.
The World Health Organization, with input from the CDC, decides what strains of influenza should go into the influenza vaccine for the upcoming flu season.
Because it takes six months to grow the influenza strains (usually in chicken eggs) that go into the vaccine, a decision for the northern hemisphere’s upcoming season’s vaccine has to be made in February.
Sometimes the experts guess correctly and sometimes they do not.
The most common injectable influenza vaccine is made by inactivating two of the agreed-upon influenza A strains that have been grown for that season along with one (called “trivalent” vaccine) or two (“quadrivalent”) strains of influenza B vaccine.
A recombinant trivalent or quadrivalent influenza vaccine is also made by taking the parts of the influenza virus strains that are needed to make people immune and getting rid of the rest of the viruses.
This vaccine has fewer side effects (fever, achiness, local soreness and redness) and can be given to children as young as 6 months old.
Another vaccine – the live attenuated intranasal virus vaccine – is made by weakening the strains of influenza virus that are recommended for that season and making them sensitive to our usual body temperature.
This vaccine is squirted in the nose, where the weakened viral strains have to stay (it is cooler there, where air is coming in and out).
According to the CDC, however, this vaccine has been all but ineffective the last three seasons (about 3% effective last season, for example).
The CDC is not recommending that it be given this upcoming (2016-17) flu season.
The injectable influenza vaccine is recommended for all children from 6 months of age and upward. It is also recommended for pregnant women, since it can protect the mother and also her young infant after birth