Thursday, February 5, 2015

What you need to know about the measles epidemic. Then relax

Measles is uncomfortable. I remember having it, and it was the worst of all my childhood diseases. It was very painful to eat and drink. Still, I was better in about a week. And then I had life-long immunity.  

What is the death rate from measles? 

By the time I had measles, in 1959, only one in 10,000 children died from it.  See the following graph from a 1972 paper, which demonstrates that by 1945, there were minimal fatalities from measles. 

There is confusion about this. It is widely claimed that one in one thousand children with measles will die. Back in the 1950s and early '60s, about 500,000 measles cases were reported yearly, and there were an average 440 deaths.  But about 4 million cases occurred yearly in the US, while most were not reported to authorities. Unlike today, there was no requirement to report cases of measles, nor did parents feel every child with measles needed to see a doctor. When only reported cases are considered, there is one death per thousand cases. But when all cases are considered, there was only 1 death in 10,000 cases of measles. However, in developing countries, where malnutrition is common and dehydration may go untreated, the death rate is considerably higher.

In 1945, penicillin was only starting to be available, and modern ICUs and ventilators did not yet exist. Instead, simple care with adequate hydration kept people alive until they got over it. This is the usual therapeutic approach to viral illnesses. Here's the proof that it works, from Measles death:case ratios, New York State,1910–1969, by decade. Reprinted from Hinman ARResurgence of measles in New YorkAm J Public Health 1972;62:498-503.

Figure 2.

Vaccine refusers are a minority of those susceptible to measles

You might be surprised to learn that vaccine refusal plays a relatively small part in the number of measles-susceptible people in the US. CDC data show the median rate of non-medical vaccine waivers in US schoolchildren was only 1.7% last year. This is less than 1.5 million children.

There are 3 other categories of children and adults who are susceptible to measles, but who are not considered vaccine refusers.  Even if every child with a non-medical vaccine waiver was required to get the MMR (measles, mumps, rubella) vaccine on time, there would still be 6-7% of Americans who could catch measles if exposed:
  • People who have survived childhood cancers, organ transplants and HIV infections, or been treated for serious autoimmune diseases, usually avoid the (live) MMR vaccine due to their weakened immune systems. They may be highly susceptible to many infectious diseases. 
  • Children under 12 months old do not receive the MMR vaccine, as it is less effective in younger age groups.  MMR is recommended between 12-15 months of age. More than 1% of Americans are simply too young to be vaccinated.
  • The MMR vaccine is between 90% and 99% effective in inducing measles immunity. According to CDC, an estimated 7% of children who receive just one MMR dose will remain susceptible to measles.  A second dose is recommended at age five. CDC reports that 3% of children who receive 2 MMR doses will still fail to be protected.  This leaves about 3% of fully vaccinated children over age five, and many vaccinated adults unprotected. (Additional MMR doses may be given at college entrance and to non-immune adults.)
How many children are unvaccinated? The number of children who, last year, failed to get two measles vaccinations by age 5 is 5.3% according to CDC. Some of them got one MMR dose. Let's estimate that parents of 5% of children, about 4 million, refused the MMR. This is likely an overestimate, when you consider that only 1.7% of students received non-medical waivers. 

Say there are up to 4 million vaccine pediatric refusers. If none of these children was exposed to anthrax or got an MMR later, there might be an additional 8 million adults who are unvaccinated. However, this total of 12 million Americans would be dwarfed by the estimated 23-47 million non-immune Americans who lack immunity for other reasons:

  1. those who failed to gain immunity after vaccination, or their immunity has disappeared over time (estimated 5-15% or 16-48 million Americans); 
  2. those who, because of treatment for cancer, organ transplant, autoimmune disease or the presence of HIV are at risk of dangerous infection from the live vaccine strains in MMR (estimated 2 million Americans, but possibly many more)*;
  3. those 5 million Americans who are too young to be vaccinated.
And sure enough, if you look at the 110 California measles cases associated with Disneyworld, you see this expected pattern:  12 children (11%) were too young to be vaccinated, 28 children and adults (25%) chose not to be vaccinated. 61 affected persons thought they had been vaccinated but this could not be documented for all. 8 possibly had contraindications to vaccination.
Let's look at measles deaths

Since 1993, I have only been able to find 3 reliable reports of deaths from measles in the United States.  (Other data suggest there might be up to 5 more cases, but I cannot find verification of them.) Deaths are extremely rare, and they are unlikely to happen to your child.  

For example, the first of the three to die was 75 years old. He was incubating measles when he entered the US from Israel.  The second was 13 years old. He developed measles after his immune system was deliberately destroyed in order to receive a bone marrow transplant. The third was a 38 year old with diabetes, congestive heart failure and COPD. All were immune compromised.

Today, there potentially might be one in 1000 deaths from measles, simply because a large portion of those who remain susceptible to measles have very serious, pre-existing medical conditions. But we simply don't know what the death rate in the US would be today, because there have been so few deaths in recent years.

Where do measles cases come from?

According to CDC, most cases of measles in the US are due to spread from imported cases. You can't stop measles without stopping travel in and out of the US.

Last year, there was a jump in cases to 644 in the US: 383 occurred as a result of Amish missionaries bringing the disease back from the Philippines. There were 23 separate measles outbreaks in 2014. Did you hear much about it? 

Despite last year's increase, over the last twenty years, on average less than one in a million Americans came down with measles yearly.

Because measles is more contagious than other common infections, when cases appear, they tend to spread. Careful case-finding and quarantines control the outbreaks. That is why we have public health professionals: to limit spread of communicable disease in this manner. The method works. Each year, small outbreaks appear and are rapidly extinguished.  For example, in 2013 there was an imported outbreak of measles in orthodox Jews in Brooklyn, New York. A total of 58 people were affected, but there was no spread outside the Jewish community.

Why is there a media frenzy over measles?

Is anything different this time to warrant the media barrage?  Not that I can tell. Only 141 people have been affected currently (and just 113 related to Disneyland), according to CDC, which is less than a quarter of total US measles cases in 2014. Is Disneyland the reason the media have hyped the outbreak? Visiting Disneyland is a rare, expensive family treat--but in this case, families got tricked. It made for an interesting story. Then, with added layers of hype and fear, the story went viral.  

The Disneyland outbreak, smaller than last year's Amish outbreak, was misleadingly spun to bulldoze the right of parents to delay or skip their childrens' vaccinations. Here's just one example, published in Forbes, and written by a scientist. Even though last year's Amish outbreak was worse, and the likely source of the epidemic was a visitor to the US, the piece blames a purported anti-vaccine movement for this outbreak: Anti-Vaccine Movement Causes Worst Measles Epidemic In 20 Years.

Soon came calls for legislation, to prevent parents from avoiding their civic duty to vaccinate.  For example:

This year’s measles outbreak has resulted in a flurry of legislative activity aimed at eliminating or making it more difficult to obtain non-medical exemptions. Such bills have been introduced in at least a half-dozen states, including California, Oregon, Maine, Minnesota, Vermont and Washington.
Yet forced vaccination still won't solve the problem of non-immune Americans. Why haven't the pundits informed themselves about this?  Why have parents been scared to death over an outbreak that is unlikely to cause permanent harm to even a single child?

Current treatments and public health programs for measles are excellent

Remember, no one has died from the current outbreak. We have excellent medical care for measles, including post-exposure vaccination for some. And if you are immune compromised, or develop a serious case, measles immune globulin is readily available, which provides the same antibodies you would develop, had you been vaccinated or previously had the disease. 

Healthcare facilities have historically been sites of measles spread. But no media are blaming them for increasing this outbreak. One advantage of the recent Ebola scare is that US healthcare facilities have gotten better at preventing the spread of viruses, including measles, within their walls. 

There has been no reduction in the rates of vaccination in the US for the past ten years.  The US Department of Health and Human Services' goal for herd immunity in its Healthy People 2020 plan is that 90% of American children receive the first MMR vaccine on time. This goal is exceeded (92%) by current vaccination rates at 19-35 months of age.  And for children entering school, 94.7% have received two doses of the MMR vaccine. We can never get this number to 100% for the reasons I listed above.

Public health policy for measles is sound.  We will always have some measles cases, but we know exactly what to do with them. The smartest thing for parents to do now is to ignore this tempest in a teapot. 

* Regarding contraindications to MMR, according to CDC reasons to avoid the MMR vaccine include pregnancy, history of allergy and many others (see here). Below are broad classes of people with immune system disorders who CDC advises should also avoid the MMR:
Immunosuppression. MMR and MMRV vaccine should not be administered to 1) persons with primary or acquired immunodeficiency, including persons with immunosuppression associated with cellular immunodeficiencies, hypogammaglobulinemia, dysgammaglobulinemia and AIDS or severe immunosuppression associated with HIV infection; 2) persons with blood dyscrasias, leukemia, lymphomas of any type, or other malignant neoplasms affecting the bone marrow or lymphatic system; 3) persons who have a family history of congenital or hereditary immunodeficiency in first-degree relatives (e.g., parents and siblings), unless the immune competence of the potential vaccine recipient has been substantiated clinically or verified by a laboratory; or 4) persons receiving systemic immunosuppressive therapy, including corticosteroids ≥2 mg/kg of body weight or ≥20 mg/day of prednisone or equivalent for persons who weigh >10 kg, when administered for ≥2 weeks (258). Persons with HIV infection who do not have severe immunosuppression should receive MMR vaccine, but not MMRV vaccine (see subsection titled Persons with HIV Infection). Measles inclusion body encephalitis has been reported after administration of MMR vaccine to immunosuppressed persons, as well as after natural measles infection with wild type virus (see section titled Safety of MMR and MMRV Vaccines) (259261).

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