A new report scrutinizing the risks of eight common vaccines is not likely to end the contentious debate about vaccine safety in Washington state, which has the highest rate in the nation of children who enter school without the required immunizations.

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A new report scrutinizing the risks of eight common vaccines is over 600 pages long, combs through more than 1,000 research papers, and is the best analysis of suspected vaccine-caused medical problems that’s ever been done, says the high-powered committee that wrote it.

Even so, it’s not likely to end the contentious debate about vaccine safety in Washington state, which has the highest rate in the nation of children who enter school without the required vaccines.

A hotly contested law passed this year bars parents from simply signing to exempt their children; starting this fall, they must include a doctor’s certification that they’ve been informed of vaccines’ risks and benefits.

Ideally, worried parents would be able to turn to such a report for answers. In some cases, the committee, convened by the Institute of Medicine of the National Academy of Sciences, delivered the goods.

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In 14 cases the panel examined, it found convincing evidence some vaccines can cause rare adverse events in certain people, including seizures, brain inflammation and fainting. Those problems were, in most cases, experienced by people with immune-system deficiencies.

The committee also found the evidence doesn’t support any connection between autism and the MMR vaccine for mumps, measles and rubella (German measles).

But in the vast majority of cases — 135 out of 158 examined — the committee couldn’t reach any conclusions about connections between vaccines and serious health conditions, saying there was insufficient evidence.

Dr. Ellen Wright Clayton, a professor of pediatrics and law at Vanderbilt University and chair of the committee, said the group wanted to be transparent and provide useful information. “We had parents in mind every single step of the way,” she said.

The report, published Thursday, is the first comprehensive look at vaccines and adverse events in 17 years.

But in a news briefing Thursday, Clayton conceded the committee didn’t answer some of parents’ most pressing questions.

For example, the committee said it did not try to determine how often such serious vaccine-caused adverse events occur.

In the report, the committee noted that many of the adverse events it examined are “exceedingly rare in the population overall,” and most often occur without being preceded by vaccination.

But in the briefing, Clayton and other committee members could not put a number on “rare.”

Without numbers, it’s impossible to compare the risk of an adverse event to the risk that an unvaccinated child might get seriously ill from a disease.

The committee also said it was not asked to answer the question “Are vaccines safe?” Nor did it have data to address the concern by many parents about multiple vaccines given at one time.

Policy decisions about vaccines, the committee said, require a “balancing of risks and benefits.”

The vaccine that racked up the highest number of problems was the varicella vaccine, given to prevent chickenpox. In some patients — most of whom had compromised immune systems — the vaccine caused brain swelling, pneumonia, hepatitis, meningitis, shingles and chickenpox itself.

The committee also found convincing evidence that the MMR vaccine led to fever-triggered seizures for some children, although those seizures rarely had long-term consequences. However, for those with severe immune deficiencies, the vaccine sometimes triggered a rare form of brain inflammation.

Both the varicella and MMR vaccines contain crippled live viruses. Vaccines that use killed virus or parts of a virus are less likely to cause problems for an immune-compromised person.

Vaccine critics, such as Marisa De Lisle, a Shoreline chiropractor and mother, noted that the committee often found insufficient evidence for a conclusion. “Just because there is no evidence, that doesn’t mean it’s safe,” she said.

In fact, said Bainbridge Island’s Michael Belkin, given the committee’s “extreme pro-vaccine bias,” its inability to prove a vaccine doesn’t cause a problem should be a “red flag to anyone who is getting a vaccine shoved down their veins by a doctor or school that insists that vaccines are perfectly safe.”

But Dr. Jeff Duchin, chief of communicable-disease control for Public Health — Seattle & King County, said the report’s message was reassuring.

“The conditions for which they found evidence are, by and large, conditions for which we were already aware” and precautions are in place, he said.

Clearly, Duchin said, the benefits of vaccines vastly outweigh the potential adverse events. Even now, there are cases of serious complications or death from vaccine-preventable diseases, he noted.

He praised the committee’s suggestions that electronic medical records be used to gather better data in the future. “Overall, it’s a good thing to have people continually scrutinize vaccines — all of our treatments in medicine — to make sure they’re as safe as possible.”

Dr. Maxine Hayes, state health officer, said risks from vaccines are far outweighed by risks from the diseases they can prevent. “Vaccines have really suffered from their own success … People have forgotten how bad these diseases can be.”

The 16 committee members included pediatricians, biostatisticians and medical doctors and researchers in several fields, including immunology and neurology.

Carol M. Ostrom: 206-464-2249 or costrom@seattletimes.com

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