Optimism remains in the face of setbacks to polio and measles elimination

August 2005

WASHINGTON – For the most part, public health officials are still optimistic that they can eliminate polio and measles despite recent setbacks in both programs.

Samuel L. Katz, MD, offered pragmatic optimism that the programs will be successful if public health officials can maintain political and societal support, as well as financial backing for the programs. During the Stanley A. Plotkin Lecture in Vaccinology at the 2005 Annual Meeting of the Pediatric Academic Societies, Katz said he is doubtful that the diseases would be eliminated in the near future, however.

Smallpox

In 1966, 170 years after Edward Jenner inoculated a boy with material taken from a cowpox lesion on the hand of a milkmaid, more than 1 million cases of smallpox were still occurring around the world. That year, the World Health Assembly pledged to eradicate the disease. Over the subsequent 11 years, health officials eradicated smallpox with a cost of about $125 million, according to Katz, who is the Wilburt Cornell Davison Professor and chairman emeritus of pediatrics at Duke University in North Carolina.

The smallpox campaign was successful for several reasons: smallpox was easy to diagnose, there were no occult patients, infection resulted in permanent immunity and there was no carrier state and no animal reservoir, according to Katz. The vaccine was heat stable, inexpensive, protected after a single dose and could be administered at any age.

“Smallpox was a plague of mankind until it was eliminated,” said Katz. “And it was the only infectious disease that we know of that has been truly eradicated.”

Polio

Buoyed by the success of the smallpox eradication effort, the World Health Assembly declared in 1988 that it would eliminate polio by 2000. At that time, polio paralyzed an estimated 350,000 people each year, but the number of cases occurring each year was much higher.

“When you count the number of cases that are reported, those are cases of paralytic disease. For everyone of them, there may be from 200 to 1,000 individuals who [have polio], who have either no overt symptoms or maybe a minor illness, so when you read the statistics today, you have to multiply those to see how many infections are actually occurring,” Katz said.

The 2000 deadline, as well as another, has come and gone, and still there is polio. The new deadline is 2006 and will require at least another $100 million.

“Will we achieve it by 2006?” Katz asked. “I’m not that much of an optimist, but some of our heroes at the CDC, lead by Steve Cochi, the person responsible for the U.S. program, are more optimistic than I.”

Eradicating polio requires social, political and financial commitment. To date, about $3 billion in public and private funds have been spent to eradicate the disease, according to Katz. The Rotary Club, which has been an active private participant, has spent about $600 million.

“By 2004, we were down to six countries where polio was still endemic. And those leading the charge were becoming increasingly optimistic that global eradication of polio was possible,” he said.

But that optimism was diminished the same year, when the number of cases went up instead of down, from 700 to more than 1,200. This occurred after tribal leaders in northern Nigeria told their people that the polio vaccine was tainted, and the eradication effort was a plot to sterilize their daughters and give their sons HIV.

“So for 11 months, they stopped using polio vaccine in northern Nigeria,” Katz explained. As a result, the surrounding countries, which had been polio free, are now seeing cases, and the cases have spread to the Middle East. Developments in Yemen and Indonesia add further pessimism to the WHO’s achievement of its 2006 eradication goal. The 440 cases reported there to date represent more than 88,888 infected individuals shedding type 1 polioviruses. The task is a daunting one, according to Katz.

“This obviously leaves a great deal of uncertainty about how far we can go with polio vaccination,” Katz said.

Still, there is hope. The number of cases is relatively small, as is the number of countries where polio is endemic. If health officials can convince people to accept vaccination, the tide can be turned, noted Katz.

On the plus side, one strain has already been eliminated. The least virulent type 2 strain no longer exists in the wild. Sanofi Pasteur has developed a monovalent vaccine that will be used in those areas that have seen an increase in cases, according to Katz.

“The type 1 vaccine is far more immunogenic than the trivalent vaccine; 81% of individuals with a single dose, not three doses, will develop antibodies,” Katz said.

Another sign of hope are the Days of Tranquility, short-term vaccination campaigns, which Katz described as a “little schizophrenic.”

“But in the Central African Republic, in the Congo, in Afghanistan and elsewhere, groups who are in armed combat have been willing with the encouragement from WHO to lay down their arms for a week to conduct campaigns for immunization. When the campaigns are over, then they start killing one another again. As I said, it is a little schizophrenic, but fortunately, it has been successful,” he said.

Measles

Due to the high mortality rate in children – between 5% and 10% — from measles in the 1960s, there was a saying in Nigeria: “Don’t count your children until measles has come through.”

“In the United States, measles was an inevitable infection of infancy in childhood, but it was not a disease that was dread like it was in resource poor countries. Nevertheless, the CDC showed that the hospitalization rate following measles was close to 20% and any complications were near 30%. Deaths were about 1 in 500 in this country,” he said.

During the 1989 to 1990 U.S. outbreak, there were 130 reported deaths from 22,000 cases. “Some of them had underlying conditions, which might have given them some immune deficits, but 92 of them were perfectly normal children.”

When the vaccine was licensed in 1963, measles was so common that 97% of children by second grade had antibodies to measles virus. Quickly, cases were controlled in the United States, and today, there is no wild measles. The only cases are importations from countries where the disease is not well controlled.

Ciro de Quadrus, who had worked in both the polio and smallpox eradication programs, spearheaded an elimination program for measles in the Americas. The Western Hemisphere became free from indigenous measles. There are still problems with importations, and countries continue to vaccinate, but measles is controlled in these countries.

“The same facilities that have been used for the surveillance of acute flaccid paralysis [for polio] have also been included in the surveillance of febrile rash disease, so they can look at reported measles cases and determine if this is measles or not,” Katz said, and they are also using Days of Tranquility for catch-up immunization.

More than 500,000 people, mostly children, died from measles in 2003, according to WHO. “Before vaccine was available, WHO estimated there were 8 million deaths of children each year,” Katz said. Forty-five countries accounted for 95% of these deaths, and 31 of these 45 countries are in sub-Saharan Africa.

Not all the importations are from resource poor countries, Katz said. Many are from industrialized countries such as Japan.

“Louis Cooper and I have visited Japan several times trying to get the pediatricians to join with the public health authorities to do something about measles. People who work there in hospitals say they have kids on ventilators, kids with encephalitis, kids in their intensive care units – why? It’s a long, complicated story, but really it is called mumps vaccine. They used measles, mumps and rubella, which had the Urabe strain of mumps that produced aseptic meningitis. That soured the practitioners and the families, so they’ve gone ahead and used nothing,” he said.

Northern Nigeria presents the same trouble spot for measles vaccine as it does for polio vaccine – its leaders lying to the people about the West using it to cause them harm. There were more than 25,000 cases of measles reported in northern Nigeria in the first four months of 2005 with more than 600 deaths. In southern Nigeria, however, there were only 253 cases of measles and no deaths.

Beyond the politics, there are other problems associated with measles elimination. “The virus is probably the most highly transmissible of those we deal ordinarily. We know you can’t give the current vaccine early on because maternal antibody aborts the effects of the vaccine. You have to give it as late as 9 months, which is when it is given in the WHO’s Expanded Program on Immunization program.

“To get rid of measles, you need a two-dose schedule, because with one dose you only get 90% to 95% of children immunized, and that 5% to 10% is a sufficient residual of susceptibility that if virus gets introduced, it finds all the susceptibles very quickly,” Katz explained.

It costs only $1.20 to vaccinate one child against measles. If one gives measles vaccine at the same time as polio vaccine, the cost decreases to about 60 cents a dose, according to Katz.

But it is hard to maintain enthusiastic support for any long-term program. After a while, people become tired, their priorities change and they no longer support the programs as fully as they did at the start. “You have donor fatigue,” Katz said.

There is still hope. In March, WHO reported a 40% drop in deaths due to measles and public health officials have targeted countries in Africa, India and parts of Southeast Asia for elimination by 2010.

Katz, who codeveloped the measles vaccine, shares their goal, but not the optimistic time frame. “As much as I would wish for the fulfillment of the 2010 goal, I really doubt this achievement will be seen even in my lifetime, but perhaps for the younger members of the audience, I hope you will all live to see that,” Katz said.

For more information:

• Katz SL. “Smallpox, polio, can measles be far behind?” The 2nd Annual Stanley A. Plotkin Lectureship in Vaccinology. Presented at the 2005 Annual Meeting of the Pediatric Academic Societies. May 14-17. Washington.