So you heard the flu shot is 10 percent effective.
With so many sources of information available, the primary care provider’s role increasingly becomes that of educator. It is important to me that the parents of my patients make informed decisions, so when I have a parent decline the influenza vaccine, I make an effort to ask why. The number one response I hear has been “What’s the point? The flu shot is only 10 percent effective this year.”
In my discussions with parents, I’ve pinpointed several issues that are raised repetitively. Here’s five of them.
1. The effectiveness of your child’s flu shot is unknown right now. Recently, the New England Journal of Medicine published an article stating that the influenza vaccine in Australia was deemed 10 percent effective. The effectiveness of the influenza vaccine can only be determined when the season is over. In the Southern Hemisphere, the flu season precedes ours occurring April to October. This is helpful as it provides a sort of preview to what our season may potentially have in store. However, because our season is not yet complete and there are differences between the population surrounding your child and the one studied in Australia no one knows the effectiveness of the flu shot that is being offered to your child. We will not know this until sometime after May 2018. We do know that our current flu shot has low effectiveness against H3N2. Australia used the same vaccine we are using, and their predominant strain was also H3N2, so the study results suggest that the flu shot will have less benefit this year.
2. Several factors contribute to the low effectiveness of flu vaccine this year. The flu virus is dynamic. As it replicates genetic changes occur that affect how the antibodies that we develop from the flu shot interact with the virus. This is called antigenic drift. The World Health Organization presents its recommendations to the Northern Hemisphere in February and vaccines are manufactured 6 to 9 months prior to flu season. That allows 6 to 9 months for the differing strains to replicate and change genes. Because of antigenic drift, it is possible that certain strains that did not exist during vaccine manufacturing are circulating now during flu season. It is also possible that though we share with Australia the same predominant H3N2 we may have other strains currently circulating that were not found in the Australian population. Unfortunately, H3N2 is difficult to vaccinate against. It has a higher rate of antigenic drift, and it undergoes more genetic changes during the vaccine manufacturing process. Suggestions are being made to change how we manufacture vaccines to reduce this problem. However, science is still working on answering all the questions around H3N2.
3. Generally, the effectiveness of a vaccine involves how well-matched the vaccine is to the predominantly circulating strain. The flu vaccine has relatively good coverage against the H1N1 strain of influenza A and strains of influenza B. Its protection against the H3N2 strain of influenza A has been consistently low. Seasons when H3N2 predominates are poorly matched seasons and tend to be severe. According to CDC studies, on a well-matched year vaccine effectiveness can range from 40 to 60 percent. During 2014 to 2015 when the poorly matched H3N2 predominated the entire season, vaccine effectiveness was estimated at 19 percent.
4. Despite factors that suggest low effectiveness of the flu shot, your child should still get vaccinated. Even though H3N2 is predominant this year, there are several other strains circulating for which the vaccine provides significant coverage. You don’t know which strain your child will get! Also if your child does get infected with influenza, his illness will be less severe than that of an unvaccinated child. This could mean the difference between a clinic visit versus hospitalization. Studies show that the vaccine confers significant protection in certain populations. It has been shown to reduce the risk of flu illness by 50% in pregnancy and reduce flu illness in your baby by 50% several months after birth. In children with diabetes or chronic lung disease, the flu shot can reduce hospitalizations. Mothers who are vaccinated can pass antibodies to their baby during pregnancy and breastfeeding. If you are having difficulty breastfeeding, vaccinating everyone in the home can protect your little one.
5. Tamiflu is not a replacement for the flu shot. Tamiflu blocks the release of more virus from the cell it has infected. This stops replication and eventually stops symptoms, shortening illness by 1 to 1.5 days. Tamiflu only works for the five days that you take it. In order for it to last through the season, your child would have to take it every day. At the recommended doses, Tamiflu is relatively safe with a low side effect profile. However, even water is toxic when you take in too much of it. This medicine has not been studied to be taken on a daily basis for months at a time.
Many times a parent will respond with “I just don’t want my child to get sick.” Let’s briefly weigh the pros and cons. The influenza vaccine has the same side-effects as school-required vaccinations, and the main contraindication is history of anaphylaxis (a severe allergic reaction) to the flu shot. Even people with egg allergy are safe to get vaccinated. The vaccine does take two weeks to build immunity (a good reason to get vaccinated early in the season), so there is a period when your child could develop respiratory symptoms, but the flu shot never gives your child the flu. If your child is already getting their routine shots, an additional flu shot is not going to increase their pain. Comparing the potential side effects from vaccination to the symptoms found in a hospitalized child or the pain from one injection to the pain from multiple injections during a hospitalization it becomes a little easier to determine the best thing for your child.
Jennifer Variste is a pediatrician.
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