Aaby, P.

Bennett, J.

Coll Seck, A.M.

Markowitz, L.

Samb, B.

Simondon, François

Whittle, H.

Horizon / Pleins textes

THE LANCET 
he concept of the study was imaginative, but jf should 
Behaviour modification to avoid HIV, transmission 
and it is coo important to be predicated on unsound “nil 
risk” conclh8ions. 
Gary Reynolds \. 
ì 
Department of Public Health Medicine. Clwyd Health Authority, Mold. 
Clwyd CH7 1 P Z .  U K  
What is soluble? 
SIR- “Science, as famously defined by Sir Peter Medawar, 
is the art of the soluble” writes a Lancet book reviewer (July 
23, p 250). Medawar answered Arthur Koestler’s question 
(in The Act of Creatioli)-why‘ did scientists not engage in 
“intense research” on “the generics of behaviour?”-by 
pointing out that “the problem is very, very difficult” and is 
unlikely to yield to “direct assault”. He went on, “No 
scientist is admired for failing in the attempt to solve 
problems that lie beyond his competence . . . If politics is the 
art of the possible, research is surely the art of the soluble. 
Both are immensely practical-minded affairs” (The An of the 
Soluble, 1967, p 87). I doubt if Medawar would have 
thought his epigram improved by the substitution of 
“Science” for “research”. The epigram o+n politics that 
inspired Medawar came from the German Chancellor, 
Bismirck in 1867. 
D I? Laurence 
i 
27 Denning Road, London NW3 lST, UK 
’\% 
)( Sex differences in measles fatality and 
Edmonston-Zagreb measles vaccine 
SIR-Dilraj and Karim (May 28, p 1366) indicate that use 
of high-titre Edmonston-Zagreb (EZ) vaccine at 6 months 
of age coincided with a significantly higher case-fatality 
ratio for girls with measles admitted to the measles 
wards at  Clainvood Hospital, Durban, South Africa, than 
for boys. However, it seems unlikely that an increase in risk 
of death from measles in girls who received high-titre EZ 
vaccine was responsible for the sex-specific difference 
observed. 
The case-fatality ratio for girls was very similar during the 
2 years before the “EZ period” and the 20-month EZ period 
(4.4% vs: 5.4%; not significant) whereas the case-fatality 
ratio for boys fell significantly (4.7% vs 1.7%; p=0.006). 
Thus, a significant reduction in the case-fatality ratio for 
boys with measles during the EZ period was mainly 
responsible for the sex differences, not an increase in case- 
fatality among girls. 
The case-fatality ratio for girls fell between the EZ 
period and the post-EZ interval of September to December, 
1992, (5.4% to 1.2%, p=0.024). Although the age at 
death of measles cases was not given, it will have 
substantially exceeded the age at  immunisation for those 
who were immunised. Thus the reduced case-fatalities 
for boys (1.6%) and girls (1.2%) in this post-EZ 
interval would have reflected, in part or perhaps even 
primarily, the mortality experience of children eligible to 
receive high-titre vaccine during the preceding 20-month EZ 
period. 
5 of 8 patients admitted during the E 2  period who had 
documentation of immunisation status had not been 
vaccinated. If this proportion is representative of all 
admissions during the EZ period, differences in sex-specific 
mortality ratios would have been determined mainly by the 
mortality experience in unvaccinated rather than vaccinated 
children. 
In our Senegal studies,’ we observed high and comparable 
vaccine efficacy on exposure to measles cases for several 
years after high-titre EZ at 5 months (92%) and Schwarz 
standard vaccine at 10 months (97%). Furthermore, we 
have observed no acute-phase measles deaths in the few 
measles cases that have occurred in Senegalese children 
vaccinated with high-titre EZ. Measles case-fatality ratios in 
Senegalese children previously vaccinated with any vaccine 
are significantly reduced (unpublished). Similar observations 
on EZ and Schwarz vaccines have been made in Guinea- 
Bissau.’ 
Coverage rates in the Natal Kwazulu region were not 
reported but coverage with measles vaccine probably 
increased during this time period due to an accelerated 
vaccination campaign,’ and the reductions in annual 
numbers of measles cases admitted to Clainvood Hospital 
suggest that this campaign was effective. As coverage 
increases so the proportion of measles cases previously 
vaccinated rises, even though efficacy remains high. An 
increase in the proportion of measles cases who were 
previously vaccinated may underlie the lower case-fatality 
ratios seen in girls and boys in the post-EZ period. 
A reanalysis of community data from Machakos, Kenya, 
shows that measles case-fatality ratios declined 
simultaneously with improved immunisation coverage with 
standard doses of Schwan vaccine at 8-9 months.’ The 
decline in case-fatality ratio was more rapid for boys, leading 
to significantly higher case-fatality ratio for girls despite a 
general decline in the severity of measles. Hence in the initial 
phase, boys in Machakos may have benefited more. We do 
not know whether these similar trends in case-fatality ratios, 
for different vaccines in different sites, were caused by the 
same factors. 
Available data on mortality in children admitted to the 
measles wards at Clainvood do not permit an inference that 
high-titre EZ was ineffective in preventing measles or that it 
was responsible for the sex-specific changes in case-fatality 
ratios. 
We doubt if the sex-specific changes in measles case- 
fatality ratios are related in any way to our observations of a 
higher incidence of non-measles deaths in girls receiving 
high-titre Schwarz and EZ vaccines at 5 months compared 
with girls given standard doses of Schwarz vaccine at 10 
months. 
The WHO Expanded Programme on Immunization, Task Force for Child 
Survival and Development (Atlanta, USA), and Science and Technology 
for Development Programme of the European Union, (TS3*-CT9 1-0002) 
conrributed financial support. 
John Bennett, Peter Aaby, Francois Simondon, Badara Samb, 
H m t t l e ,  Awa Marie Col/ Seck, Lauri Markowitz 
I ’  
Task Force for Child Survival and Development, Atlanta, Georgia 30307, USA; 
Danish Epidemiology Science Centre, Statens Seruminstitut, Copenhagen: 
UR Maladies Infectieuses et Parasitaires, ORSTOM. Dakar. Senegal: 
MRC Laboratories. Banjul. The Gambia: UniversitB Cheikh Anta Diop, Dakar: 
and Centers for Disease Control and Prevention, Atlanta 
1 Aaby P, Samb B, Simondon F, et al. Sex specific mortality after 
high titre measles vaccines in rural Senegal. Bull IVor/d Health Organ 
(in press). 
2 Aaby I?, Knudsen K, Whittle H, et al. Lang-tem survival after 
Edmonston-Zagreb measles vaccination: increased female mortality. 
JPediurr 1993; 122: 904-08. 
3 Abdool Karim SA, Abdol Knrim Q, Chamane M. Impact of a measles 
immunization campaign on measles admissions to 3 Natal hospital. 
S Afr MedJ 1991; 80: 579-81. 
4 Aaby P, Leeuwenburg J. Sex and pattems of transmission of measles 
infection: 3 reanalysis of data from the Machakos area, Kenya. 
Ann Tmp Pediutr 1991; 11: 397402. 


Sex differences in measles fatality and Edmonston-Zagreb measles vaccine

Abstract

Similar works

Full text

Available Versions

Horizon / Pleins textes