VOA标准英语2012--Study Shows PFCs Can Reduce Vaccine Effectiveness

Study Shows PFCs Can Reduce Vaccine 1 Effectiveness

When children are vaccinated 2 their immune systems produce antibodies that protect them from debilitating 3 and potentially deadly childhood infections, such as polio, measles 4, diphtheria and tetanus. The protection is supposed to last a lifetime.

But scientists say the effectiveness of these vaccines 5 is severely 6 reduced when children are exposed to high levels of PFCs:

“This was quite serious because we could also see some of the children were so low in antibody concentration that they were essentially 7 not protected. They have been vaccinated four times and vaccines had not worked,” said Dr. Phillipe Grandjean of the Harvard School of Public Health.

Grandjean led a team of scientists in a study of children living on the Faroe Islands between Scotland and Iceland.

The islanders were chosen as subjects because their diet is mainly seafood 8, known to have high concentrations of PFCs.

The scientists followed a group of more than 500 children who'd been vaccinated against diphtheria and tetanus. But children who showed elevated levels of PFCs in their blood also had very low concentrations of antibodies against these infections.

“It was quite a striking fact, one that I would not have anticipated,” said Dr. Peter Hotez, president of the Sabin Vaccine Institute, which promotes vaccine development and delivery around the world.

Hotez said if PFCs do, in fact, interfere 9 with antibodies and immune system functions, then the public health problem is going to be much worse in the urban slums of low- and middle-income countries, where exposure to these industrial chemicals can be much higher.

“Even a modest reduction in vaccine coverage 10 and vaccine immune responses could lead to subsequent outbreaks of childhood disease. And there is a risk that we could see recurrences 11 of childhood killers 12 such as diphtheria or pertussis or other childhood diseases now becoming more common in the world’s poorest countries,” said Hotez.

Scientists say PFCs are stable and persistent 13 chemicals that have been in wide use for decades - so much so that everyone probably has detectable 14 levels of the compounds in their body.

“We have not done enough in regard to protecting the population against these old compounds, and now we are stuck because we all have them in our bodies and we are all using them,” said Grandjean.

Critics note that since the study was done on island residents eating a mostly fish diet, it should have taken into account polyunsaturated fatty acids [PUFAs], which are found in fish and may suppress the immune system.

Researchers say there is an urgent need to study the adverse 15 health effects of perfluorinated compounds on larger populations.