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Monday, May 7, 2012

Whooping cough outbreak was only a minor problem, thanks to vaccines

David Brooks

When New Hampshire reported a spike in cases of whooping cough among schoolchildren last November, on the heels of a similar report from Vermont, some people feared the worst.

The worst is happening in Washington state, which is facing a localized whooping cough epidemic, with hundreds of children falling ill, in part, because of people avoiding vaccinations.

More on that in a minute, but first let’s enjoy our good news – well, sort of good.

It turns out that virtually all of the roughly 60 pertussis cases reported throughout Hillsborough County in late fall of 2011 were in children who had been properly vaccinated, said Marcella Bobinsky, head of the state’s immunization section, and the outbreak didn’t spread.

“It has been calm since then,” said Bobinsky.

The vaccination news is good because it reflects the state’s relatively high rate of immunizations, but it’s bad because it shows that our control of whooping cough, officially called pertussis, still leaves much to be desired.

The disease, named because it leads to a deep, persistent cough, kills about 300,000 children a year in the developing world. It hasn’t been a serious problem in the U.S. for more than a half century because of vaccination, but in recent years, the number of cases has been creeping up, partly because the disease seems to be developing new strains that resist vaccines.

Bobinsky said the issue is the longevity of antibodies created by the vaccine called TDAP (tetanus, diptheria and pertussis).

TDAP is given in a series of shots up to age 1, and the state says children should get a booster at age 11. But there are increasing indications that protection “wanes more quickly that they would like it to,” said Bobinsky; much of New Hampshire’s outbreak was in children around ages 9 and 10, whose immunity from vaccines had faded.

Medical officials will now have to consider whether to tweak their TDAP recommendations, perhaps moving up the booster.

That’s a decision that carries lots of hidden consequences and can’t be taken lightly; the continuing debate over whether to recommend meningitis vaccines for infants – an issue debated in an unusual federal hearing held by the Centers for Disease Control in the state last June – reflects how hard it can be to balance health cost and benefit.

But as I said, there is some relative good news: We’re not like Washington state.

That state has reported 1,100 cases of whooping cough so far in 2012, double the usual number for an entire year. At least 20 infants have been hospitalized, although happily nobody has died, and the state expects to see the most cases of the disease since before World War II. They are spending millions of dollars in emergency funds to fight the disease.

This is at least partly due to the spread of the evolving disease, since similar outbreaks have been seen on the West Coast, but a contributing factor is Washington’s high rate of people who don’t vaccinate their children for a variety of medical, philosophical and religious objections.

The vaccine-avoidance rate for kindergartners is a whopping 6 percent in Washington, the highest rate in the country. In some counties, the rate approaches about 1 child in every 13, to the point that “herd immunity” is eroding.

Herd immunity is the rather inelegant term for the fact that if most of the people around you are vaccinated against a disease, that disease probably can’t get a toehold in the area. Therefore, you are indirectly protected even without a vaccine.

This is why people who shun vaccines, usually because of misplaced medical fears, often get away with it. (While we’re on the topic: no, vaccines don’t cause autism, contain rat poison or overwhelm your immune system. Yes, they are imperfect, as the situation with pertussis shows, but doing without them would be vastly worse, as a stroll through medical literature from a century ago will demonstrate.)

Loss of herd immunity doesn’t seem to be a concern in New Hampshire, where only 1.9 percent of kindergarten students have a religious exemption from the requirement that they be vaccinated against 10 diseases before entering school. There are also a small number of medical exemptions.

Thankfully, New Hampshire doesn’t allow parents to claim a philosophical exemption, which usually means “I’m worried about something I saw on the Internet and figure everybody else’s vaccination will keep my kid safe.”

Let’s hope it stays that way. Personal freedom is at the heart of what it means to live in New Hampshire, but not if it endangers other people, especially children.

Granite Geek appears Mondays in the Telegraph, and online at www.granitegeek.org. David Brooks can be reached at 594-6531 or dbrooks@nashuatelegraph.com.