The co-developer of a vaccine for rotavirus, the leading cause of severe diarrhea in children, Offit is chief of the division of infectious diseases at Children's Hospital of Philadelphia. His books include Vaccines: What You Should Know and Autism's False Prophets: Bad Science, Risky Medicine, and the Search for a Cure. This is the edited transcript of interviews conducted on Dec. 30, 2009 and March 2, 2010.
One hundred years ago, what infectious diseases would a baby born in Philadelphia face?
So 100 years ago in Philadelphia, you still saw diseases like yellow fever. Diphtheria was the most common killer of teenagers. Hepatitis B virus would infect tens of thousands of children, frankly, every year. ...
Measles would cause 100,000 people to be hospitalized, primarily children, and between 500 to 1,000 to die. Rubella was a very common cause of congenital infection, meaning that the mother would be infected while the baby was still in the womb, resulting in about 20,000 cases every year in the United States of birth defects such as those that involve the eye, the ear and the heart. It was a terrible time. We lived 30 years less ... than we do now, in large part because we didn't have the vaccines that now can save our life.
Did we still have smallpox then?
1900, yeah. There was still smallpox in the United States really up until the 1940s. ...
What's contained these scourges? What's been the great breakthrough?
Vaccines.
How did it do this? Is it the mass immunization, use of vaccines?
Yes. Because viruses or bacteria are spread from one person to the next, the only way in which you can really effectively stop transmission is to vaccinate a critical number of people in the population. And it depends really on the nature of the virus or bacteria as to how many you need to immunize.
For a disease, for example, like measles, which are highly contagious, you need to immunize probably between 90 to 95 percent of the population to really stop transmission cold. ... Every year in the United States, about 60 to 65 people come in from outside of this country, primarily Western Europe, who have measles.
And it's very rare actually that measles will spread from one American child to the next, because we have a critical number of people in the United States that are vaccinated. That wasn't true in 2008, when a child who was unvaccinated went to Switzerland, caught measles, came back to the U.S., and then there were several cycles of transmission from one American child to another to another to another. That level of transmission hadn't been seen for more than a decade. It's what made it so frightening.
That was an indication that San Diego had lost its herd immunity?
That's exactly right. And I'll give you an example [of] exactly how contagious measles virus is. There was a girl who was part of a church group in Indiana, who went to Romania, where she proceeded to catch measles, although she didn't know it. She got on a plane; she came back, where she then walked among a group at a church picnic of about 500 people. Of those 500 people, 465 had either been previously immunized with measles or had had measles. Of that group of 465, only three people got measles.
Of the remaining 35 who hadn't been vaccinated, 31 caught measles. Thirty-one of 35 people who hadn't been vaccinated caught measles in a crowd of 500 people after being exposed to a woman for only a couple hours, and the reason why is that they didn't have to have direct contact with her. All they had to do was share her air space within two hours of her being there.
Over time, the number of vaccines that children get has increased. Compare what you had as a child with what's on the schedule now.
I was born in 1951. I got the smallpox vaccine. I also got the diphtheria and pertussis and tetanus vaccine. And then in the mid-1950s, I got Jonas Salk's inactivated polio vaccine. And that was it.
Now how many does a baby face?
Now, in the first few years of life, babies will receive vaccines to protect against 14 different diseases.
This seems like a crowded schedule. They get multiple shots sometimes?
That's right. You can get as many as 26 inoculations in the first few years of life, and as many as five shots at one time.
That seems like a lot of vaccines. Are they all necessary and safe?
Yes. I certainly understand from a parent's standpoint how the schedule is crowded. I think from the pediatrician's standpoint, the schedule is crowded. It's a lot of vaccines given over a fairly short period of time, which can mean a lot of shots at one time. But I think the burden for health care people and for people interested in people's health is to make sure that the vaccines can be given safely, and that we know that they will prevent these diseases that can cause suffering and hospitalization [and] death.
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