In pediatricians’ offices across the country, it is once again the time each year when we see children and families getting ready for school: having their well-visit and annual check-ups if it’s been a year or more since the last one, and of course, inquiring about flu vaccines – not just for children but for the entire family – and vaccinations in general.  Below, I’ve answered several questions I get asked quite often.  I hope I answer some of your questions, as well.

My family and I had a flu vaccine last year – why do we need a flu vaccine again this year?  I heard the strains of flu in the vaccine are the same as last year.

Every year, CDC influenza experts look at which strains of the flu virus are circulating worldwide and use that information to predict which strains are likely to predominate in the US during the upcoming winter flu season.   Their predictions are correct most years.  Vaccine manufacturers then make a vaccine which contains the 3 most likely strains.  Most years, at least one of the strains changes from the previous year’s vaccine, but occasionally the strains are the same.  This year’s vaccine strains are the same as last year’s.  So why should you get the flu vaccine this year if you had it last year? 
Unfortunately, immunity wanes over the course of a year, so it’s necessary to get vaccinated again even if you got vaccinated last flu season.

Is it ever too early to get the flu shot?  

No.  Immunity typically lasts for 8-9 months, and is reliable for six months at least.  Flu tends to start increasing in late November or early December and lasts at high levels through March, dwindling into April.  Thus, getting immunized in October or November is ideal.  However, it’s still reasonable to get immunized in September, especially if you happen to be in the office for another reason.  

When is it too late to get the flu shot?

Flu circulates at high levels through March and well into April.  It probably takes around 2 weeks for the vaccine to create full protection. Thus, it still makes sense to get immunized at least through the end of March. 

I’m allergic to eggs and I hear that the flu vaccine is made from eggs. Can I get the flu vaccine?

Flu vaccine is made in chicken eggs.  However, flu vaccines vary in the amount of residual egg protein in the final product.  Manufacturers measure that egg protein so we know which flu vaccines are safe for egg-allergic patients.  Sometimes, people who’ve had very severe (anaphylactic) allergic reactions to eggs need to be referred to an allergist to determine whether they can safely receive the flu vaccine.  

How can I learn about vaccine safety in general?   I’ve read a lot in the media about a million different things being blamed on vaccines.  Most of the accusations I’ve read seem flimsy, but I’d like to know more.  How can I educate myself about this?

A number of excellent information sources are available.   The Vaccine Education Center at the Children’s Hospital of Philadelphia provides a series of web pages (also available as printed, one-page information sheets) about each currently available vaccine and about common vaccine-related questions and concerns.

The Immunization Action Coalition also has high quality information on vaccines and vaccine safety for patients and parents.  

An excellent book was published several years ago by Martin Myers, a vaccine expert, and Diego Pineda, a science journalist.   The book, Do Vaccines Cause That?! A Guide for Evaluating Vaccine Safety Concerns, is a clear and thoughtful look at how medical research can prove or refute causation.  The first half of the book examines the issues in general, including risk perception, risk communication and statistical approaches to determining causality, and attempts to demystify immunology for the average reader.  It also addresses the crucial issue of how a non-expert reader can judge the quality of information they’re reading.  Finally, there is discussion of the generic categories of criticism which opponents use to attempt to discredit vaccines. 

The second half of the book then proceeds to apply those principles to examine many specific accusations leveled against vaccines, including allegations that vaccines cause or worsen asthma, autism, autoimmune diseases, and more.   It’s a great tool to help you understand these controversies.

Of course, your primary care team is perhaps one of the fastest and easiest sources for vaccine information.   Nurses often have particular expertise in vaccines, so please ask them your questions or concerns – we’re all here to help!

Dr. Ben Kruskal is a pediatrician at the Somerville practice and an infectious disease specialist. He is the Director of Infection Control and Travel Medicine at Harvard Vanguard Medical Associates. Dr. Kruskal went to college at the University of Pennsylvania and attended medical school at New York University. He did his pediatric residency and pediatric infectious disease fellowship at Boston City Hospital (now Boston Medical Center). Dr. Kruskal served on the faculty at Children's Hospital and Massachusetts General Hospital before he joined Harvard Vanguard in 1997. He collaborates with researchers at Harvard Medical School's Department of Population Medicine, focused chiefly on the use of electronic systems for disease surveillance. Dr. Kruskal has co-authored twenty peer-reviewed publications and a book chapter. He is passionately interested in quality of care and patient safety, and has served on Harvard Vanguard's Quality Assurance Committee since 2000. As a pediatrician, Dr. Kruskal garners a lot of credibility when patients learn he has five children.