A hot news story this fall was from California, where students were forced to get the pertussis booster vaccine or they won’t be allowed in school. This new law was pushed because of a pertussis epidemic which has already killed 11 children, especially in areas like Marin county where vaccination rates had slumped. I’m a big fan of vaccines, and it’s clear to me and my colleagues that vaccines have been, and continue to be, one of the fundamental medical advances of the last few hundred years. But we are increasingly fighting a media war against the anti-vaccine crowd, and vaccination rates are dropping in some areas, often with predictably disastrous results as we now see in California.

We doctors now always need be on alert to counter the many anti-vaccine arguments, and now we have a major reinforcement in a new evidence-based  review of the 8 most common vaccines. This very important report is from the US Institute of Medicine, which is considered the gold-standard of objective, evidence-based reviews upon which many countries base their medical care. Or to put it another way — many lawsuits regarding vaccines would use IOM reports as their top evidence. (Here is the link to the IOM report, called “Adverse Effects of Vaccines: Evidence and Causality”.)

The most important take-home message from this study was that “the M.M.R. vaccine doesn’t cause autism, and the evidence is overwhelming that it doesn’t,” according to Dr. Ellen Wright Clayton, the chairwoman of the IOM panel. To put it more dryly, the IOM states, “evidence favors rejection of five vaccine-adverse event relationships, including MMR vaccine and autism and inactivated influenza vaccine and asthma episodes.” This certainly isn’t the first time scientists have found no link, but hopefully this IOM report can be the final nail in the coffin of the MMR-autism allegations.

So that’s the good news; the less good news is that there are some adverse reactions, sometimes severe, which vaccines can cause. The most concise review of the report’s pros and cons is from a Medscape report:

The IOM group decided that the evidence “convincingly” supports a link between

• anaphylaxis and MMR, varicella, influenza, hepatitis B, meningococcal, and tetanus toxoid vaccines;
• febrile seizures and MMR vaccine (such seizures almost always have no long-term consequences);
• syncope and the injection of any vaccine;
• deltoid bursitis and the injection of any vaccine;
• disseminated Oka-strain varicella zoster virus, along with Oka-strain varicella zoster virus viral reactivation (both with and without other organ involvement) and varicella vaccine; and
• measles inclusion body encephalitis and MMR vaccine in individuals with severe immune system deficiencies.

According to another set of committee conclusions with a lower certainty level, scientific evidence favorsaccepting a causal relationship between

• anaphylaxis and HPV vaccine,
• transient arthralgia in adult women and MMR vaccine,
• transient arthralgia in children and MMR vaccine, and
• a mild and temporary oculorespiratory syndrome and certain trivalent influenza vaccines in Canada.

Conversely, the committee stated that the evidence favors rejecting a causal relationship between

• type 1 diabetes and MMR vaccine;
• type 1 diabetes and diphtheria, tetanus, and pertussis vaccine;
• Bell’s palsy and inactivated influenza vaccine;
• asthma exacerbation or reactive airway disease episodes and inactivated influenza vaccine; and
• autism and MMR vaccine.

In its deliberation on MMR vaccine and autism, the committee stated that it reviewed 22 studies for epidemiologic evidence but relied only on 5 that, unlike the others, were “reasonably valid” overall. Each of the 5 studies asserted that there is no causal relationship between the vaccine and autism.

The committee also reviewed 4 articles and weighed evidence for the biological mechanisms by which MMR vaccine could possibly trigger autism. Its report noted that one of those articles, authored by the controversial Andrew Wakefield, was retracted last year by its publisher, The Lancet. Earlier this year, a series of articles and editorials in the British Medical Journal called Wakefield’s article an “elaborate fraud.”

“The committee assesses the mechanistic evidence regarding an association between MMR vaccine and autism as lacking,” the report stated.

There was also a good review of this important research by the The New York Times, which mentioned how the chicken pox (varicella) vaccine can sometimes cause problems as adults:

The panel did conclude, however, that there are risks to getting the chickenpox vaccine that can arise years after vaccination. People who have had the vaccine can develop pneumonia, meningitis or hepatitis years later if the virus used in the vaccine reawakens because an unrelated health problem, like cancer, has compromised their immune systems.

The same problems are far more likely in patients who are infected naturally at some point in their lives with chickenpox, since varicella zoster, the virus that causes chickenpox, can live dormant in nerve cells for decades. Shingles, a painful eruption of skin blisters that usually affects the aged, is generally caused by this Lazarus-like ability of varicella zoster.