Measles

It looks like the H1N1 pandemic is fading fast. I am amazed at how lucky we were, at least in the hospitals where I work. A month ago all the ICU beds were full, most of the ventilators were in use and we were wondering how we were going to triage the next batch of patients who needed advanced life support and we had none to offer. Then, right as we reached maximum capacity and had no more wiggle room, the rates plummeted. We skated right up to the edge of the precipice, looked down, and did not have to jump.

The pandemic has not been as bad as expected, but it was still no walk in the park. Nationwide H1N1 killed maybe 10,000, with 1,100 in children and 7,500 among young adults (ref). Oregon has had 1200 hospitalizations and 68 deaths. We had about 8 deaths from H1N1 in my hospital system. We would have had twice that number, but one of our hospitals is a trauma center and offers ECMO (Extra Corporeal Membrane Oxygenation) and we managed to save a number of people who would have died if they had been in a lesser hospital. The national statistics mirror our experience. None of the deaths were in the elderly. Pity the vaccine was slow to be produced as it could have prevented the majority of those deaths.

Are we done with H1N1? Will it become part of seasonal flu? Will it have a third comeback, fueled by holiday travel? Will it mutate and increase virulence? Will it recombine with avian flu to generate a new strain? Is this THE pandemic that comes every 30 years or so, and we will not see another until after I am long dead?

How am I supposed to know? I can’t see the future. Or can I? Mr. Randi, listen up: I am thinking I will be eligible for that million dollar prize. I am receiving future information from the Large Hadron Collider, curiously delivered inside a baguette. I think I can predict the next infection to sweep the US.

Measles.

Easy call, huh?

I have seen a grand total of one case of measles in my career. It was in an unimmunized young male who picked up measles traveling to Africa. I had not expected to see another case thanks to immunization. I am no longer certain that will be the case.

Measles, due to the rubeola virus, is a typical virus, with the usual fever, cough, runny nose, red eyes and a generalized, maculopapular, erythematous rash. One of many childhood infections that have plagued mankind. Measles is very infectious, with 90% of household contacts exposed developing the disease. It is one of those infections that is easy to acquire in the waiting area of a doctors office.

Case fatality rates in the West are low, about 0.3%, while in the third world it kills up to a third of infected children. About one in a thousand get encephalitis.

In the old days, everyone developed measles with about 3 million cases a year, with relatively little, but devastating, morbidity and mortality.

“Before measles vaccine, nearly all children got measles by the time they were 15 years of age. Each year in the United States about 450 people died because of measles, 48,000 were hospitalized, 7,000 had seizures, and about 1,000 suffered permanent brain damage or deafness.”

Much of this is preventable by the vaccine. No vaccine is perfect, and the measles vaccine is no different. Measles vaccine is about 90-97% effective in preventing infection, depending on the population studied. Or to think of it another way, 3 to 10% of the population would remain susceptible to the disease even if we had 100% of the population vaccinated.

Thanks to Dr. Andrew Wakefield, fear of MMR induced autism is highest in Great Britain and as a result measles vaccination rates have fallen. Perhaps it should now be Mediocre Britain, at least where vaccines are concerned.

Vaccination rates have fallen in England, and at one point 20% of children were susceptible to measles, mumps and rubella. Since the English refer to vaccination as ‘the jab’ I am surprised they get anyone to take the vaccine. It’s like referring to colonoscopy as riding the python. Who would want that?

“A particularly significant decline was observed between 2000 and 2004, which can arguably be attributed to deterioration in public confidence about the safety of the MMR (Reference).”

As a result, measles boomed.

All due to Dr. Wakefield’s report in the Lancet, which evidently should have been published as work of dark humor in Punch.

“More importantly, the controversy appeared to affect parental decision-making. Uptake rates for MMR in England fell from 87.4% in 2000-01 to 79.9% in 2003-04, the lowest figure at any time since the widespread introduction of the triple vaccine in 1990-91. The decrease was especially significant given that the single vaccines alternative was only available from private medical clinics, at a cost of around £200.

The Wakefield study has been widely discredited, and MMR uptake has recovered to an extent: in 2007 vaccination rates stood at 84.6%. Meanwhile, measles notifications in 2006 and 2007 were the highest for almost a decade. (Reference)”

I wonder, as an aside, about responsibility. One of the refrains of the antivax crowd is that big pharma is protected from any liability from vaccine injury. Big pharma cannot be held responsible. I wonder, when the causes of autism are finally elucidated and vaccines are definitely exonerated as we have the answers to the etiology of autism, if Dr. Wakefield, AoA and Ms. McCarthy will assume the responsibility and liability for all the morbidity and mortality their actions caused. I am sure they will happy to step up to the plate and offer restitution to the affected families.

There was, of course, another paper out of Poland, “Lack of Association Between Measles-Mumps-Rubella Vaccination and Autism in Children,” this month exonerating the MMR as a cause of autism. Poland has an interesting history with regards the measles vaccine:

“The MMR vaccine was introduced in Poland later than in most other European countries. For the past 10 years, the MMR vaccine has been gradually replacing the single-antigen measles variety. When it was first introduced, MMR was not covered by the national health service of Poland. Parents who wished to vaccinate their children with MMR, as opposed to the single mandatory measles vaccine, had to pay extra. For this reason, few children were immunized with MMR. The Polish mandatory vaccinations schedule did not include MMR for all children until 2004.”

As a result,

“Poland’s heterogeneous population (ie, vaccinated with MMR, vaccinated against measles only, nonvaccinated) serves as a unique sample group for studying the debated association of these vaccines with autism in children.”

In comparing the three groups they found no association between MMR and autism. None. In fact, they found “a lower risk of developing autism for children vaccinated against measles, with the lowest risk being found for children vaccinated with MMR.”

This finding is dismissed by the authors as perhaps

“the decreased risk of autism among vaccinated children may be due to some other confounding factors in their health status. For example, health care workers or parents may have noticed signs of developmental delay or disease before the actual autism diagnosis and for this reason have avoided vaccination.”

Dr. Gorski also thought the finding was a fluke. Part of the argument against MMR being protective being that having one child in the family with autism would make it unlikely for other children in the family to get the vaccine out of fear of the vaccine causing autism when, in fact, it is due to perhaps inherited causes. The lack of vaccination actually being a marker for families with other predispositions to developing autism.

I am not certain that is true. As the authors report:

“This serves as evidence that, despite extensive media coverage of the debated association between MMR and autism, public acceptance of this vaccine remains very high. The situation in Poland is different to that of many European countries, where MMR vaccinations by age 2 years fell more than 10% and were followed by measles outbreaks. In this time, Poland’s already high rate of measles immunization even slightly increased.”

Seems that the Poles were immune to the anti-MMR hysteria, although I cannot say with certainty. If so, then the finding of the protective effect of vaccination, given the study population, may be valid.

Me? I think everything is due to an infectious disease. Infections are the One True Cause of All Disease. While this is the first study to demonstrate the protective effect of the MMR, remember that measles, mumps and rubella are neurotropic viruses with encephalitis a known complication. There has long been a suspicion of viral infections altering the brain to unmask schizophrenia and there is an association between borna virus and OCD. Could a subtle neurologic infection exacerbate a predilection towards autism? I do not think it is out of the question. But that is my delusion.

Vaccination rates have fallen in some segments of the US population as well. In the US, low vaccination rates are found primarily in the children of the well-to-do and often are clustered in alternative schools. There are dozens of schools with vaccination rates under 80%, with some schools having vaccination rates of 5% (reference).

Well, fine, you may say to yourself: they can get the measles or other vaccine preventable diseases. At least it will stay in the those enclaves of unvaccinated children. My kids are vaccinated and in schools where vaccine rates are high. My kids are safe. I would have thought the same thing.

Herd immunity and the models that try and predict what levels of immunity are needed to protect a population are based on the assumption that unimmunized people are randomly distributed in a population, not clustered in alternative schools.

In the Journal of Infectious Diseases this month is a description of a measles outbreak in Canada where clusters of unvaccinated populations helped perpetuate a measles outbreak even though overall community vaccination rates were high (“Long-Lasting Measles Outbreak Affecting Several Unrelated Networks of Unvaccinated Persons”):

“Despite a population immunity level estimated at ∼95%, an outbreak of measles responsible for 94 cases occurred in Quebec, Canada. Unlike previous outbreaks in which most unvaccinated children belonged to a single community, this outbreak had cases coming from several unrelated networks of unvaccinated persons dispersed in the population. No epidemiological link was found for about one-third of laboratory-confirmed cases. This outbreak demonstrated that minimal changes in the level of aggregation of unvaccinated individuals can lead to sustained transmission in highly vaccinated populations. Mathematical work is needed regarding the level of aggregation of unvaccinated individuals that would jeopardize elimination.”

The graphic shows how schools acted to magnify the epidemic:

The isolated measles virus was genotyped and almost all isolates were identical, demonstrating how infectious measles can be with what was presumptively minimal contact.

As the discussion said:

“An important assumption of mathematical models predicting elimination, however, is the random distribution of susceptible persons in the population. In reality, unvaccinated individuals are not distributed at random. Religious groups opposed to vaccination are often tightly knit communities. Our outbreak involving 2 unrelated alternative schools attended by children whose parents were resistant to vaccination on philosophical ground demonstrated that these persons also aggregate. The spontaneous interruption of this outbreak, despite the current level of aggregation in unvaccinated children, suggests that endemicity was not likely to be reestablished in this population. The continued propagation throughout many generations of cases, however, raised the possibility that a minimal change in the overall vaccine coverage in the population or in the level of aggregation of unvaccinated individuals can lead to sustained but protracted transmission despite an immunity level near 95%.”

Lest you think this outbreak epidemiology is limited to measles, the US northeast experienced a similar outbreak with mumps, where clusters of unvaccinated populations help magnify the spread of disease.

A child with mumps came to the US from, hey, I’ll be damned, England, thank you Dr. Wakefield, where, thanks to low uptake of the MMR (the second M standing for mumps) there is a mumps epidemic. The index case went to a religious camp and gave it to the other campers, who in turn went to other collections of unvaccinated people to start their own epidemic and so on. In this case there was little spread into the wider community that “might be attributable to generally high vaccination levels and little interaction between members of the affected religious community and persons in surrounding communities.”

It appears that collections of unvaccinated people may serve to magnify the ability of diseases to spread in a community. Those unvaccinated children in the alternative schools may be unlikely to keep their infections to themselves.

My million-dollar prediction? Measles will be imported into the US in a student from Mediocre Britain. That student will visit an alternative school and start an epidemic in the school. Measles will be spread from school to school and into the community and will be difficult to control.

It will occur in 2012. The Mayans, along with the other indigenous peoples in North and South America, were killed by the millions by vaccine preventable illnesses like measles, pertussis, mumps and smallpox. The real reason the Mayan calendar ends in 2012 is the end of the world will be due to the return of vaccine-preventable diseases.