POST 01081E : BCG EFFICACY QUESTIONED
Follow-up on Posts 01070E
(http://listes.ulaval.ca/cgi-bin/wa?A2=i ... org&P=1144)
(http://listes.ulaval.ca/cgi-bin/wa?A2=i ... .org&P=406)
18 April 2007
NOTE : The link to the PATHâ€™s evaluation of a new
refrigerator, in the previous posting didnâ€™t
correspond exactly to the documentâ€™s name on the
site. My apologies! It is now corrected and the
document can be downloaded without any problem.
Interestingly, I found out that the reasearch
which was the topic of the news in the first
posting of this series, originated in a previous
research ten years ago at Stanford University, in
which Pr. Behr was also involved. For those
interested, you can visit the following link, for more information.
"Study Casts Doubt on Effectiveness of TB
Vaccine" by Dr. Peter Small and Dr. Marcel Behr
This posting contains two contributions. The
first is from Robert Steinglass
IMMUNIZATIONbasics in the USA. The second is a
official WHO response made jointly by Diana Chang
Blanc (mailto:ChangBlancD@who.int), from
WHO/IVB/EPI and Ulli Fruth
(mailto:firstname.lastname@example.org), from WHO/IVB/Initiative for Vaccine Research
I added some more information and links at the bottom of this posting.
It has long been known that BCG vaccines vary
greatly in their proven efficacy against
pulmonary TB from one area of the world to the
next (India, USA, elsewhere). WHO has emphasized
for a long time that BCG is primarily used
because of its proven efficacy against the more
dangerous fatal types of TB - miliary and meningeal TB in infants.
By the way, there is published data on the
efficacy of BCG against leprosy (I vaguely recall
from Malawi about 10 years ago, and perhaps elsewhere).
My concern is that, with web chatter,
anti-vaccination groups can seize on information
such as the low efficacy of BCG against pulmonary
TB. This is why a communications strategy is
important at global and country level to
anticipate mischief and provide tools/messages to
health workers at various levels to deal with it.
I hope the authors clearly distinguish between
BCG and other vaccines when they broadly say that
"Vaccines administered to infants today have
never been tested, it is not the same product
anymore, says Professor Behr. All these vaccines
are thus of unknown effectiveness."
WHO has an excellent web site on vaccine safety
(Immunization safety :
http://www.who.int/immunization_safety/en). I am
not sure what their policies are regarding
responding to every serious (or frivolous) report
concerning unsafe vaccines. As of early April, I
did not see any posting related to this recent
article on BCG. Perhaps WHO would be able to
inform TECHNET readers in countries about
suitable responses to this particular claim against BCG.
WHO deems the currently available BCG vaccine
safe and continues to recommend that a single
dose of BCG be given to neonates as soon as
possible after birth in countries with a high
prevalence of TB, as well as to infants and
children in countries with low endemicity of
tuberculosis if they are at increased risk of
exposure. While numerous efficacy studies
demonstrate that the current vaccine does not
have a significant impact against pulmonary
disease (the most common manifestation of the
disease), it offers considerable protection
against life-threatening TB meningitis and
disseminated TB disease among infants and young children.
The vast majority of BCG vaccinations given
worldwide are derived from the French Pasteur
strain 1173 P2, the Danish strain 1331, the Glaxo
strain 1077 and the Tokyo strain 172. In terms
of efficacy, there is not overwhelming evidence
that one strain is demonstrably better than
another and there is currently no global
consensus on which BCG strain is most
optimal. While a recent case-control study
conducted in South Africa (Mahomed H, Kibel M et
al, Pediatr. Infect Dis J. 2006; 25 (12):1166-72)
demonstrated that intradermal immunization with
the Danish 1331 strain resulted in slightly lower
rates of disseminated TB (meningitis and/or
miliary spread) than percutaneous immunization of
children with the Tokyo strain 172, both strains
proved equally effective in preventing against
all manifestations of TB in children. Moreover,
the observed protective efficacy against
disseminated TB in the combined BCG vaccinated
cohorts exceeded 75%, as compared to the non-vaccinated cohort.
Furthermore, with increased understanding of the
immunological deficiencies of BCG vaccine and
advances in mycobacterial genome analysis,
promising new products may be forthcoming. In
fact, several approaches to develop new TB
vaccines are underway, with 5 candidate vaccines
currently in early clinical trials. These are
either live mycobacteria ("improved" BCG or
rationally attenuated M.tuberculosis) or subunit
vaccines containing one or several TB antigens.
If any of these first generation vaccines prove
efficacious, licensure can be expected around 2015.
In 2004, WHO published a BCG vaccine position
paper in the Weekly Epidemiological Record which
provides a detailed summary of key information on the disease and the vaccine.
BCG Vaccine : Position paper (January 2004)
Original English and French versions [pdf 468kb]
at : http://www.who.int/immunization/wer7904 ... _paper.pdf
For further information, the link also provides a
partial list of references upon which the
position is based. (http://www.who.int/immunization/Refs_BCG_May_1_2006.pdf)
Diana Chang Blanc, IVB/EPI
Ulli Fruth, IVB/Initiative for Vaccine Research
NOTE : I didnâ€™t find any material on protection
by BCG against leprosy in Malawi but in India.
"Effectiveness of bacillus Calmette-Guerin (BCG)
vaccination in the prevention of leprosy; a
case-finding control study in Nagpur, India", by
Zodpey, Sanjay P, Shrikhande, Sunanda
N, Salodkar, Atul D, Maldhure, Bhagirath
R, Kulkarni, Shyam W. ; International Journal of
Leprosy and Other Mycobacterial Diseases, Sep 1998.
Maybe some members can share other articles they are aware of.
Another article may also interest members. This
is : "BCG vaccine effectiveness in preventing
tuberculosis and its interaction with human
immunodeficiency virus infection", by MarÃa
Patricia ArbelÃ¡ez, Kenrad E Nelson and Alvaro
MuÃ±oz ; International Journal of Epidemiology 2000;29:1085-1091.
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POST 01081E : BCG EFFICACY QUESTIONED
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