Transcript BCG Vaccination

BCG Vaccination
Dr Lika Nehaul
CCDC / NPHS TB Programme Lead
Wales Immunisation Conference 2008
Acknowledgements
• Nature (Scientific) Publishing Group
• Health Protection Agency
• World Health Organisation
Aspects covered
• A brief reminder of some basic facts about
TB
• The origins of the BCG vaccine
• Efficacy of BCG, and its contribution to
tuberculosis control
• BCG policy and its implementation in
Wales
• TB vaccine developments
Tuberculosis caused by mycobacteria
species
• Mycobacterium tuberculosis causes vast majority
of cases
• Mycobacterium bovis causes <1% of confirmed
infections in the UK
• M. africanum a very rare cause
• Some other mycobacterial species can cause
pulmonary disease resembling TB, referred to as
atypical mycobacterial infection
Natural history of tuberculosis
• Only between 5 & 10% of people with primary
infection develop clinically apparent disease
• In some individuals the immune system appears
to overcome infection
• In others the bacteria are held in check (latent
TB infection) and can then reactivate in later life
causing post-primary pulmonary TB
• Tubercle bacilli contracted by the inhalation of
M.tuberculosis bacilli in droplet nuclei
Summary of tuberculosis epidemiology
• About one-third of the world’s population
thought to be infected with M. tuberculosis
• Nearly 9 million new (incident) cases each year
• 2 million deaths per annum
• WHO declared TB a global emergency in 1993,
but incident cases still increasing year on year
Efficacy of BCG – clinical trials
• Formal clinical trials only started in the late 1930s
• Protective efficacy varies from world region to region –
from 70 – 80% to none at all
• Inadequate protection against infectious, post-primary,
pulmonary TB in adults
• Protection shown to last for 10 to 15 years (JAMA 2004 –
some protection up to 60 years)
Reasons for observed variations in efficacy
• Differences in potency of various strains of
BCG
• Genetic or age differences in different
populations
• Reduced virulence of some strains of M. tb
• Prior exposure to non-tuberculosis
mycobacteria
• (?Methodological problems with some trials)
BCG vaccine is good at:
• Protection of neonates and children
against serious forms of primary disease
such as meningeal and disseminated TB
• Protecting against death
Tuberculosis ( all forms )- Notifications, annual totals
England and Wales 1913 - 2000#
Chemotherapy
BCG vaccination
Year
Port Health Authorities not included - 1913-1938 classified as pulmonary TB
Figures for 1982 onwards exclude notifications for chemoprophylaxis
# Data for 2000 provisional
Source: Statutory Notifications to the Communicable Disease Surveillance Centre
Notification rate per 100,000
Notification rates of all forms of
TB in males in 1953 and 1999
200
180
160
140
120
100
80
60
40
20
0
1953
1999
<15
15-24
25-34
35-44
45-64
>65
Age groups
PHLS
TB in England, Wales & NI -2005
Controlling tuberculosis
• Early diagnosis and prompt treatment
especially of pulmonary disease
• Use of observed / supervised treatment
where necessary
• BCG vaccine
BCG Policy in the UK
• JCVI advises UK Health Departments on
immunisation policy
• Welsh Assembly Government agreed to changes
to BCG Immunisation Programme recommended
by JCVI in Summer 2005
• JCVI recommendations should be followed
rather than NICE TB Guidelines for BCG
• TB Chapter in Green Book updated on line in
November 2007*
*see home page: www.dh.gov.uk
Recommendations for BCG
• Infants living in an area of the UK with an
incidence of TB of 40 / 100,000 or greater
• All infants, children and young people aged up
to under 16 years of age with a parent or
grandparent born in a country where the annual
incidence is 40 / 100,000 or greater
• Previously unvaccinated, tuberculin negative,
contacts of cases of respiratory TB (follow NICE
TB Guideline)
Recommendations for BCG (con)
• Previously unvaccinated, tuberculin-negative new
entrants under 16 years of age who have lived for a
prolonged period (at least 3 months) in a country with a
high TB incidence
• Individuals at occupational risk (page 397, TB Chapter
(Nov 2007), Green Book (note advice on HCWs)
• Travellers and those going to work abroad: may be
required for previously unvaccinated, tuberculin
negative, individuals aged under 16 going to live or work
with local people in a country with a high incidence of TB
• Where vaccine requested: assess for specific risk factors
for TB
Guidance on BCG Immunisation
• WHC 2005 (062): Changes to BCG Immunisation
Programme, 8th July, 2005
• WHC 2005 (077): Guidance on changes to the
BCG vaccination programme, 6th September,
2005
• NPHS has prepared a ‘Framework Document for
BCG Vaccination of infants and children up to
under 16 years of age in Wales’
Guidance on BCG (con)
• BCG Programme in the UK now risk-based
the key part being a neonatal programme
targeted at those children most at risk of
exposure to TB
• Schools programme ceased from
September 2005, but LHBs, in liaison with
RICs, required to make alternative
arrangements to protect at-risk children
who will no longer be covered by the
schools programme
TB vaccine developments
• Candidate antigens- secreted and surfaceexposed antigens
• Enhanced potency BCG, using antigen 85B
(recombinant vaccine)
• Subunit vaccines
• New strategy could involve using a priming
recombinant vaccine, and boosting the immune
response