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Commentary on W.P. 2.1, The Measles Epidemic of 1968

Terence Turner

Department of Anthropology

Cornell University

April 19, 2002


Some members of the El Dorado Task Force have reportedly opposed the idea that James Neel intended or used the vaccinations against measles administered by the 1968 AEC Orinoco expedition for a research-related purpose, on the grounds that they were not integrated into an experimental design with a control group and testing of reaction levels at a later date. Neel's and his colleagues' own writings contradict this interpretation. They show, firstly, that while recognizing that proper experimental design was impracticable under the circumstances of their work on the Orinoco in 1968, they nevertheless maintained that the vaccinations could provide general and fundamentally important research findings; secondly, that they did carry out limited testing of resistance levels (antibody titres) at periods up to 11 months after the administration of the vaccinations; and thirdly that they contemplated repeating similar vaccination campaigns in the hope of yielding theoretical "reevaluations" of the Yanomami's genetic capacity for resistance to these diseases. The major text for this purpose is Neel, James V., Willard Centerwall, Napoleon Chagnon, and Helen Casey, "Notes on the effect of Measles and Measles vaccine in a virgin soil population of South American Indians." American Journal of Epidemiology 91 (1970):418-29.

This paper is a research report of the theoretical implications of data collected by the expedition on the 1968 measles epidemic, extending to include testing of small numbers of subjects up to 11 months following the return of the expedition in April 1968. Commenting on the uncontrolled and fragmentary nature of their data, Neel et al. make clear that they regard the conditions of working with the Yanomami as precluding the possibility of a "proper" experiment. As they say,

"Parenthetically, a proper study of the comparative response of a truly primitive group and a group of civilized controls to measles vaccine and the disease itself, which would involve a series of comparable age and sex distribution observed under identical conditions, will probably never be possible." (421)

Despite their recognition of the impossibility of controlled experiments under Yanomami conditions, however, they nevertheless conducted follow-up blood testing on some groups of Yanomami, and drew general research conclusions from the results. According to them, the results of these tests confirmed Neel's basic theory that Amerindian groups have substantially equal genetic capacity to generate antibodies in response to "civilized" epidemic diseases as Caucasians. This was a research finding of great importance to Neel. Towards the end of the article is a small section entitled, "A
small-scale serologic follow-up". It begins,

"Serologic follow-up studies have been possible in two villages only. Blood samples were collected in 1969 from individuals in village A, which had been given vaccine with MIG [i.e., gamma globulin--TT] 11 months previously and had enjoyed 100 per cent protection, and from unvaccinated individuals in village E who had experienced approximately a 100 per cent attack rate 11 months previously. The antibody titers from these groups are shown in table 4. All sera tested showed measles HI antibody ...on the basis of this very small series, the ability of the Indian to form antibodies to an antigen to which he may not have been previously exposed appears no different from that of the much-exposed Caucasian." (426-427)

In the next section, "Discussion", Neel et al. make the following points:

"The combined evidence suggests that the reaction of the Indian to measles vaccine is somewhat greater than that of Micronesians, Africans, or United States Caucasians... However, although this greater "reactivity" could be a genetic phenomenon, the "average" Yanomama differs in so many acquired characteristics from the "average" individual in the series with which the Indians are being compared, that much of this difference could be due to secondary factors ...There is thus in our opinion only very limited evidence for a greater innate susceptibility of the Indian to this disease...It is in this connection noteworthy that the antibody response of the Indian to measles seems very similar to that of the Caucasian. A reevaluation is probably in order with respect to the primary susceptibility of the Indian to certain other diseases of civilization, such as pertussis, smallpox and tuberculosis." (427-428).

Neel makes essentially the same point about the theoretical implications of the effects of the epidemic, considered as an "experiment of nature" in his autobiography. It is clear that Neel thought that research findings of great general importance could come from uncontrolled, not "properly" experimental contexts like the measles epidemic, and/or vaccination campaigns, which would permit relatively small samples of individuals whose history of exposure or vaccination could be known to be tested for antibody levels. The results obtained from such tests were sufficient for him to make general inferences about the confirmation of his theoretical hypotheses, as the passages quoted from the present article attest.

This is clearly the level at which Neel thought of vaccination campaigns as forming part of his research agenda. If further support for this inference were needed, it is pertinent that the diseases of pertussis (whooping cough), smallpox and tuberculosis, which Neel mentions as standing in need of "reevaluation" (i.e., study through the same means as his "reevaluation" of measles through the vaccinations), are those he mentions, along with measles, as the objects of vaccination campaigns in correspondence with potential
vaccine donors before leaving for the Orinoco in 1968. This interpretation of Neel's research interest in vaccinations is consistent with humanitarian medical values and in no way precludes them.

Here are two other relevant sources, one from Neel's field notes from the collection of his papers in the Archive of the American Philosophical Society and one a short text by Willard Centerwall delivered as part of a symposium on epidemic diseases among indigenous and other isolated populations after the expedition's return from Venezuela:

1) On a loose piece of note paper in Neel's handwriting from his papers from the American Philosophical Society Archive, entitled "Ocamo Follow Up", he lists 18 individuals (designated by numbers)with four dates on which blood was drawn from them: 22 Feb 66, 17 Feb 68, 18, April 68, and 9 Feb 69. Under each date is a column with numbers entered for each of the 18 individuals. I don't know what the numbers mean, but the clearly refer to the blood that was drawn. Underneath the four columns are written the words: "Mix of previous measles, gg [gamma globulin] inj[ections], vaccination, mild measles."

2) In his article, "A recent experience with measles in a 'virgin soil' population", Willard Centerwall says:

"Observations on these Yanomami Indians of the effect of the wild measles vaccine with and without the concomitant gamma globulin form the basis of this report (p. 143)...the use of the measles vaccine permitted us to see some of its effects on the Indians. In villages where we could observe and measure the effects at their height, we found...considerable reaction, especially in terms of febrile response. That this response was associated with the production of protective measles antibodies was borne out clinically." (p.144)

The "clinical" confirmation to which Centerwall refers is presumably the same as the follow-up testing mentioned in the Neel, Centerwall, Chagnon and Casey article.

These data are consistent with and are reinforced by statements by Neel collaborator Francisco Salzano and others reported in my posting, "Turner on Turner* on Turner, Point by Point by Point" (3/20/02) on the AAA El Dorado Task Force web page ( http://www.aaanet.org/edtf/index.htm ) and on this website ( http://www.gettysburg.edu/~choward/yanomami-responses/turner.html ).