Friday, October 22, 2010

And So It Begins

CDC, Public Health Image Library
I am fortunate to have the Dengue Vaccine Initiative as a client. Through this group, I have traveled the world, meeting with doctors and scientists, working to lay the groundwork for a coming vaccine against dengue fever. As our work has progressed from discussing issues with surveillance and diagnostics, we have moved into communication issues - the need to raise awareness among politicians, healthcare professionals, and consumers of a coming vaccine, and the lifesaving (and cost saving) benefits such a vaccine will confer on countries in which dengue sickens hundreds of thousands of people annually.

One of the issues that confronts us is anti-vaccine activism. This is a worldwide phenomenon. Activists' concerns range from what we see in the United States - concerns about autism - but also include cultural-specific worries. For example, in Argentina, a branch of the Catholic church warns that vaccines will cause women to abort their fetuses. In parts of Asia with large Muslim populations, there are concerns that some vaccines are made with cells from dogs or from pork gelatin. It is stiff opposition that can usually be satisfied with factual answers.

But overall, countries outside of the United States are hungry for vaccines. When PATH and The Gates Foundation worked with India to quickly distribute a vaccine against Japanese Encephalitis - a mosquito-borne disease common in rural areas that causes paralysis and death in high numbers - they were able to vaccinate 32 million children in a year and a half because people were desperate for protection. From the safety of the United States, it may be difficult to understand that polio still cripples hundreds of children in India each year or that measles killed over 160,000 people worldwide in 2008. We have become used to a childhood without those terrible diseases.

This is likely a generational issue. My mother remembers having to stay indoors during the hot summer months, away from other people, when polio epidemics were raging throughout the countryside. Isolating her family was the only way my grandmother could protect her children.  As a kid, probably around 3 years old, I stood in line in a school gymnasium - a very long line snaking around the gym and outside the door - to receive a dose of the Sabin polio vaccine on a sugar cube. I have a fuzzy memory of the darkness of the gym but really what I remember is the solemnity of the occasion. Granted, it was a long time ago, but I like to think I was feeling the resolve of all those moms who brought their kids in to protect them against the seasonal fear of fever, paralysis, iron lungs. And I, too, am part of the generational divide: I have a round and dimpled scar on my upper left arm from a smallpox vaccination, a badge that signifies me as a woman of a certain age, to be sure, because today's kids don't get vaccinated against smallpox because it is no longer a threat.

Unlike smallpox, most vaccine-preventable diseases are not eradicated, just kept under control. That control, however, is tenuous because we rely on herd immunity - keeping a high proportion of our population vaccinated in order to prevent diseases - to protect our society. In other words, all those families who don't vaccinate their kids can be reasonably assured that their kids won't get childhood diseases because so many other families do vaccinate their kids. However, there is always a tipping point, where diseases can race through unvaccinated kids and infect those with partial immunity, such as the elderly who have lost their immunity, children who have not received boosters, or infants who have not received vaccinations.   Recent news carried a report of a death from whooping cough, not in Nigeria, not in Bangladesh, not in Cambodia. But here, in the great state of California. And it's the 10th one in California this year. This infant's death is attributed to families not vaccinating their children against pertussis, thus allowing this potentially deadly disease to spike again.

Recent estimates show that over 7.0% of children entering kindergarten in Marin county, a wealthy suburb of San Francisco, have waivers exempting them from childhood vaccinations based on their parents' beliefs. A private school in San Diego reports that 51% of its kindergartners had such exemptions. These are shockingly high numbers because once these percentages reach the tipping point, we will lose our herd immunity. And evidence is growing that we are approaching that that point: For each one percent increase in exemptions at a school, the risk of having a pertussis outbreak went up by 12%, a 2000 study in the Journal of the American Medical Association found. The study, which was conducted in Colorado, also found that at least 11% of the vaccinated children in measles outbreaks were infected through contact with somebody who was exempt.

Epidemics start with a whisper. A case of pertussis here, a few cases of measles there. But make no doubt about it: we are on the cusp of an epidemic of many diseases that we thought we left behind. What is it about human nature that makes us reinvent the wheel again and again? If you don't want to vaccinate your kids, I recommend you travel to poor countries around the world. Tell a mother who fears seasonal outbreaks of diseases that you turned down the opportunity to vaccinate your kids against those diseases. Of course, many who don't vaccinate their kids point out that we don't live in developing countries, and that many vaccine-preventable diseases are rare in the United States. That is true. These diseases are rare because people vaccinate their kids. And they won't stay rare if we don't.