New York: Public health officials in the US are exasperated by their inability to persuade more parents to vaccinate their children, saying they’re dealing with a small minority who are misinformed — or merely obstinate — about the risks of inoculations.

Those parents contend they have done their own research and they believe the risks are greater than health authorities acknowledge. They say they are merely making their own medical choices.

That leaves public health officials struggling to find ways to get their message across. “As scientists, we’re probably the least equipped to know how to do this,” Stephen Morse, a Columbia University infectious disease expert, said.

Most parents do bring their children for shots, and national vaccination rates for kindergarteners remain comfortably above 90 per cent. Experts aren’t even sure the ranks of families who don’t vaccinate are growing to any significant degree.

But in some states, the number of parents seeking exemptions from school attendance vaccination requirements has been inching up. In some communities, large proportions of household skip or delay shots. The rise has come despite unsettling outbreaks of some vaccine-preventable diseases that had nearly disappeared from the US.

“Part of the reason everyone is so concerned about this is because they don’t know whether things will get worse,” Dr Walter Orenstein of Emory University, considered one of the nation’s leading experts on vaccines, said.

Measles is a leading worry. A little more than 50 years ago, measles caused nearly a half a million illnesses in the US each year, including about 450 deaths. But decades of vaccination campaigns put an end to home-grown measles transmission by 2000. Annual reported illnesses dropped as 34, in 2004. But in the last five years or so, cases jumped back into the hundreds as infected travellers sparked outbreaks in poorly vaccinated communities.

Right now the number of cases remains relatively small. But health officials fear that if the number of unvaccinated families keeps growing, sustained spread of measles will be re-established in the US, and it will become a native virus once again.

‘Corrective information’

Scientists have long assumed the problem is that some parents are simply misinformed, and providing them “corrective information”, will clear things up.

But some studies have shown that doesn’t seem to work. For example, in the last 15 years, a leading concern of many vaccine opponents is that shots trigger autism in children. One recent study found that some vaccine-opposed parents could be presented with medical evidence disproving that, and seemed persuaded. But they also said they still did not intend to vaccinate their kids.

“People are really good at coming up with reasons to believe what they already believe,” Jason Reifler, a political scientist at the University of Exeter who co-authored the study, said.

In fact, vaccines can have side effects — very severe ones, in extremely rare cases that doctors can’t always anticipate. “It may be one in a million or one in 2 million, but I can’t tell you that it won’t happen to your child,” Morse said.

Parents have been nervous about vaccines for as long as vaccines have been around — at times with good reason. More than 100 years ago, vaccines were unregulated and could be as likely to harm a child as protect them. Opposition seemed to plummet for several decades, as vaccines got better and succeeded in beating back diseases that had long terrified families, including polio, measles and whooping cough.

But parental concern has seemed to be on an upswing in the last 20 years.

Cost factor

Family decisions about vaccinations have always involved a cost-benefit analysis, in which parents weight the danger of the disease against side effects or other potential risks from the vaccine itself. As overall vaccination rates hit high levels and diseases became rare, some families have decided the risks of vaccination outweigh the benefits to their children, observed Massachusetts General Hospital’s Dr Stephen Calderwood, president of the Infectious Diseases Society of America.

Another strategy is to simply make more parents vaccinate, through a concerted effort to eliminate philosophical exemptions to vaccinations or to make the exemption application process more difficult. Several experts interviewed believed reducing exemptions is the most practical approach, in a country where individual freedoms are sometimes celebrated at the expense of the communal good.

“No other country relies on mandatory vaccinations as significantly as the US does to insure high rates of vaccination,” said Jason Schwartz, a medical historian who studies vaccine policy at Princeton University. “One argument is we need those mandates.”