It’s not uncommon to hear of flu shot recipients coming down with symptoms immediately after receiving their flu vaccine or influenza shot, and you yourself may even have become ill after your last flu vaccination shot. While the flu shot is a life-saving barrier against the worst effects of influenza, it is far from an all-round guard against respiratory illness. It is entirely possible to get sick after a flu shot, for a number of reasons.
Flu shots or flu jabs typically take around two weeks to provide full immunity to the virus, and if you are exposed to influenza during that two-week period (or right before getting the shot), you may still catch the virus. As a result, many individuals who become ill during this period believe it to be a result of the influenza shot, even though flu vaccines cannot directly make you sick.
Many other illnesses have similar symptoms to the flu, such as the common cold, pneumonia, bronchitis, and stomach flu. These, however, are not affected by the flu shot. Flu vaccines are prepared yearly by a panel that determines which strains are most likely to infect the most people and are tailored specifically to those strains. Thus, each vaccine is highly specialised and must be administered at the start of each new flu season.
While unlikely, it is possible to catch another strain of flu that is not protected against by the vaccine. Alternatively, you may be one of the rare and unfortunate individuals who does not react fully to the flu vaccine. Either way, even if you do catch the flu, your symptoms will likely be much weaker than if you had never been vaccinated.
All individuals over the age of 65 are considered to be at a much higher risk of contracting the flu and should be vaccinated yearly. While the flu vaccine begins to lose effectiveness among older age brackets, flu shots can prevent anywhere from 30 to 70 percent of pneumonia and flu hospitalisations among the elderly who do not reside in nursing homes and lack chronic illnesses. For those who do qualify for either of these conditions, the vaccine can prevent 50 to 60 percent of hospitalisations and roughly 80 percent of deaths resulting from the flu. Note that it is also important for any caregivers to similarly be vaccinated in order to reduce the risk of viral transmission.
Children under the age of five are also considered to be high-risk individuals. Young children do not have fully developed immune systems, and those under the age of six months cannot receive the flu vaccine at all. Vaccinations are important for parents and children alike so that neither can transmit the virus to the other. The vaccine prevents roughly 66 percent of infections in young children, a ratio that rises as children grow older.
If you fell ill this year despite getting vaccinated for the flu, your distrust of the vaccine is entirely understandable. Keep in mind, however, that the vaccine is most likely doing its job just fine, and will continue to do so in the future. You may have been spared the flu this year without even knowing it. Getting vaccinated each season is always a good idea, to protect both you and those around you unless you have been medically advised against the shot.
Aitor is a Registered Nurse (AHPRA registration NMW0001159845) with over 17 years experience in General Nursing, Emergency Nursing and Corporate Health. He loves Flu, works with Flu, studies Flu, writes about Flu and ironically, he’s had the Flu.
He is the Nurse Consultant at Corporate Care and a proud member of the Australian National Padel Team.
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