A few facts about measles need to be told. Measles is not rapidly expanding in the US or internationally, and CDC says the rate of vaccination for measles has been stable since 1994. (However, in some states, like Oregon, the number of vaccine waivers has tripled to 6% in about 10 years. In response, last March Oregon tightened its rules for vaccine exemptions, requiring parents to be educated about vaccines before refusing.) The following comes exclusively from the CDC and WHO.
1. No one has died in the US from an acute case of measles since 2003. Because Snopes claimed this was a lie, I checked with the measles experts at CDC, who wrote me the following email today:
"Good Afternoon,
Thank you for your inquiry regarding measles deaths. Measles data available to the public can be found in www.cdc.gov/measles, MMWR (http://www.cdc.gov/mmwr/), and other publications such as those listed on http://www.cdc.gov/measles/resources/ref-res.html.
The last documented deaths in the US directly attributable to acute measles occurred in 2003. Before the measles vaccination program started in 1963, we estimate that 3-4 million people got measles each year in the US, and 400-500 of those died (http://www.cdc.gov/measles/about/faqs.html).
Kind Regards,
Division of Viral Diseases
Centers for Disease Control and Prevention"
2. Worldwide, according to the WHO, measles deaths were reduced by 74% between 2001 and 2010.
The majority of measles deaths occurred in India and Africa where not enough children are being vaccinated. India accounted for 47% of all measles deaths, followed by the entire African region at 36%...
“This is still a huge success,” study author Peter Strebel, a measles expert at WHO, told the AP. Strebel said the 85% vaccination coverage rate is the highest ever recorded.
3. Almost all recent Disneyland-related US cases (110 through February 8) have occurred in California residents, with only 17 cases from other states, Canada and Mexico.
4. Over half the cases have occurred in adults. The median age of recent measles cases is 22.
5. Only 28 (25%) of the cases were vaccine refusers. From CDC:
"As of February 11, a total of 125 measles cases with rash occurring during December 28, 2014–February 8, 2015, had been confirmed in U.S. residents connected with this outbreak. Of these, 110 patients were California residents. Thirty-nine (35%) of the California patients visited one or both of the two Disney theme parks during December 17–20, where they are thought to have been exposed to measles, 37 have an unknown exposure source (34%), and 34 (31%) are secondary cases. Among the 34 secondary cases, 26 were household or close contacts, and eight were exposed in a community setting. Five (5%) of the California patients reported being in one or both of the two Disney theme parks during their exposure period outside of December 17–20, but their source of infection is unknown. In addition, 15 cases linked to the two Disney theme parks have been reported in seven other states: Arizona (seven), Colorado (one), Nebraska (one), Oregon (one), Utah (three), and Washington (two), as well as linked cases reported in two neighboring countries, Mexico (one) and Canada (10).
Among the 110 California patients, 49 (45%) were unvaccinated; five (5%) had 1 dose of measles-containing vaccine, seven (6%) had 2 doses, one (1%) had 3 doses, 47 (43%) had unknown or undocumented vaccination status, and one (1%) had immunoglobulin G seropositivity documented, which indicates prior vaccination or measles infection at an undetermined time. Twelve of the unvaccinated patients were infants too young to be vaccinated. Among the 37 remaining vaccine-eligible patients, 28 (67%) were intentionally unvaccinated because of personal beliefs, and one was on an alternative plan for vaccination. Among the 28 intentionally unvaccinated patients, 18 were children and ten were adults...
Do you have any insight as to the source of the Chicago outbreak? I had heard an older sibling to one of the babies had had a MMR then not a word. This is all could find. http://www.nbcchicago.com/news/health/Another-Measles-Case-Confirmed-in-Cook-County-Bringing-Total-to-10-291423281.html
ReplyDeleteThe Chicago outbreak is unrelated to the Disney outbreak in California. (Last year there were 23 separate outbreaks in the US.)
ReplyDeleteOften the source cannot be found; when sources are discovered, most come from overseas.
It is true that a form of measles can spread from someone recently vaccinated, but this is believed to be only a risk for serverely immun-compromised individuals.
According to a WHO expert paper http://www.who.int/immunization/sage/7._Measles_post_eradication_risk_analysis.pdf
"There is no published conclusive
evidence for currently licensed live attenuated vaccine viruses reverting to wild‐type transmissibility
or virulence. On the contrary, the vast majority of evidence points to an impressive level of genetic
stability. However, since they are live viruses that replicate within vaccine recipients, the remote
possibility must exist that they could revert to wild‐type characteristics."
Would this qualify as published evidence of the measles virus reverting to virulence? It happened 37 days after injection, DNA test confirmed vaccine strain. http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20649
ReplyDeleteThe person involved had measles strain virus. From a quick read, it seems the illness was related to the vaccine virus rather than a more virulent version of the virus, suggesting there was a problem with the host response leading to prolonged growth of virus even 5 weeks post vaccination, and a lack of immunity sufficient to protect against it at a time when antibodies and T cells should have developed.
ReplyDeleteI would need to compared the entire viral genome to the vaccine strain genome to be sure there was no reversion.
MN
Thanks for your answer Dr. Nass. If I understand correctly, you mean it is possible that the patient has developed a measles infection, with all the classical symptoms, from the attenuated vaccine-strain, without it having reverted to full virulence?
ReplyDeleteThat was the conclusion of this paper. The authors could not identify an immune disorder in the child who got measles. The authors suggest exploring whether her two additional vaccinations played any role in her case of measles.
ReplyDelete"... Based on our review of the literature, this report documents the first case of MMR vaccine-associated measles, 37 days post-immunisation, well beyond 21 days and the routine 30 days post-MMR immunisation period used by the Canadian adverse event following immunization (AEFI) surveillance system...
Clinically significant vaccine-associated illness is rare, but when it occurs it is indistinguishable from wild-type measles, except by genotyping [8]... Complications from vaccine-associated measles have been documented in both immune-competent and compromised individuals."
On further reflection, this vaccine strain may have reverted to virulence. Since we have no information yielding its entire genome, we do not know if it remained identical to the vaccine strain. We only know it was not a wild-type measles virus.
ReplyDeleteThanks for your great question.