BCG Vaccine Assessment: Mantoux Testing, Contraindications and What to Check Before Vaccination
BCG vaccination is different from many routine vaccinations.
For some people, the appointment involves more than checking vaccination history and giving an injection. Previous tuberculosis exposure, immune status, travel history and sometimes a Mantoux test need to be considered before vaccination.
This is particularly relevant for healthcare workers, travelers and families seeking BCG vaccination before spending time in countries with a high incidence of tuberculosis.
What does BCG protect against?
The BCG vaccine is used to reduce the risk of tuberculosis disease.
Tuberculosis is caused by Mycobacterium tuberculosis and is usually transmitted through the air from a person with infectious pulmonary or respiratory TB.
The vaccine has an especially important role in protecting young children against severe forms of tuberculosis, including TB meningitis and disseminated or miliary TB.
BCG is not routinely given to the entire Australian population because Australia has a relatively low incidence of tuberculosis.
Instead, vaccination is targeted towards people whose circumstances place them at greater risk.
Who may need BCG vaccination in Australia?
According to the Australian Immunisation Handbook, BCG vaccination is recommended or may be considered for selected groups.
These include certain young children at increased risk of TB exposure and some healthcare workers with a high occupational risk of exposure, particularly to drug-resistant tuberculosis.
Young children travelling to high-TB-incidence settings may also be candidates for vaccination following an individual risk assessment.
BCG vaccination is therefore based on risk rather than simply being part of the routine vaccination schedule for everyone.
Why is an assessment needed before BCG vaccination?
BCG is a live attenuated vaccine.
Before vaccination, the clinician needs to establish that the vaccine is appropriate and safe for the individual.
The assessment may consider:
- age
- previous BCG vaccination
- country of birth
- previous residence overseas
- recent and previous travel
- known TB exposure
- previous Mantoux results
- previous diagnosis of latent or active TB
- immune status
- medications
- pregnancy
- other vaccinations
Some people will also require a tuberculin skin test before BCG vaccination.
What is a Mantoux test?
The Mantoux test is another name for a tuberculin skin test or TST.
A small amount of tuberculin purified protein derivative is injected into the skin.
The injection site is then assessed after the appropriate interval by a trained healthcare professional.
The clinician measures the area of induration, which is the firm, raised reaction beneath the skin. Redness alone is not what determines the result.
The result can provide evidence that the person’s immune system has previously encountered tuberculosis-related antigens.
Does everyone need a Mantoux test before BCG?
No.
Current Australian guidance recommends determining the need for pre-vaccination tuberculin skin testing according to an individual risk assessment.
Factors that may indicate a need for testing include whether the person:
- was born in a TB-endemic country
- previously lived in a TB-endemic country or region
- travelled to a TB-endemic region
- had close contact with a person with tuberculosis
- had close contact with someone being investigated for TB
The Australian Immunisation Handbook defines a high-incidence setting for relevant BCG travel recommendations as more than 40 TB cases per 100,000 population per year.
What happens if the Mantoux test is positive?
A positive tuberculin skin test is not a reason to simply proceed with BCG vaccination.
It may indicate previous infection or another cause of tuberculin reactivity and requires appropriate clinical interpretation.
According to the Australian Immunisation Handbook, a person with a TST result of 5 mm or greater in this pre-BCG context should be considered for further investigation of latent or active tuberculosis.
The important point is that BCG is a vaccine, not a treatment for existing TB infection.
What is latent tuberculosis?
A person can become infected with Mycobacterium tuberculosis without developing active tuberculosis disease.
This is known as latent tuberculosis infection.
Someone with latent TB usually:
- feels well
- has no symptoms of active TB
- is not infectious
- may develop active TB later
The risk of progression depends on several factors, particularly immune status and certain underlying medical conditions.
Identifying latent TB can therefore be clinically important in its own right.
Who should not receive BCG vaccination?
Because BCG contains live attenuated organisms, there are important contraindications.
Australian guidance identifies several situations where BCG should not be administered.
These include significant immunocompromise and pregnancy.
BCG is also contraindicated in people who have previously had tuberculosis or have a positive tuberculin skin test meeting the relevant threshold.
Clinical assessment is particularly important for people receiving medicines that suppress immune function.
Patients should provide the clinician with an accurate list of medications and relevant medical history before vaccination.
What about pregnancy?
BCG vaccination is contraindicated during pregnancy under Australian recommendations.
Although BCG has not been shown to cause fetal harm, live vaccines are generally avoided during pregnancy.
Someone planning international travel while pregnant should discuss their TB exposure risk with an appropriately qualified healthcare professional.
Can BCG be given with other vaccines?
Timing matters, particularly with other live vaccines.
BCG can be administered at the same time as other live parenteral vaccines.
If they are not given on the same day, an interval of at least four weeks is generally required between BCG and another live parenteral vaccine such as MMR, varicella or yellow fever.
Inactivated vaccines can be administered at the same time as, or at any time in relation to, BCG.
People preparing for international travel should therefore organise their vaccination assessment early enough to allow appropriate scheduling.
How is BCG vaccine administered?
BCG is administered by intradermal injection.
This means the vaccine is injected into the superficial layers of the skin rather than into the muscle.
In Australia, BCG should be administered by healthcare professionals trained in the intradermal vaccination technique.
The usual site is the upper arm.
The Australian Immunisation Handbook specifies a dose of 0.05 mL for infants younger than 12 months and 0.1 mL for children aged 12 months or older and adults.
What happens to the injection site after BCG vaccination?
The local reaction following BCG is quite different from the reaction seen after many other vaccines.
A small red papule usually develops.
This can subsequently ulcerate before gradually healing and leaving a small scar.
According to the Australian Immunisation Handbook, ulceration typically develops within approximately two to three weeks following vaccination and heals over the following weeks.
Some swelling or tenderness of nearby lymph nodes can also occur.
Patients should receive advice about the expected reaction and when an injection-site problem should be medically reviewed.
Should a Mantoux test be done after BCG to check whether it worked?
No.
Routine tuberculin skin testing after BCG vaccination to demonstrate immunity is not recommended.
The size of a person’s tuberculin reaction following vaccination does not reliably indicate how well they are protected against tuberculosis.
Do you need another BCG vaccine if you had one as a child?
Usually not.
BCG revaccination is generally not recommended because evidence has not demonstrated sufficient additional protection from routine repeat vaccination.
A clinician should assess the person’s vaccination history rather than automatically administering another dose.
How early should travelers arrange BCG vaccination?
Do not leave the assessment until the final few days before departure.
The Australian Immunisation Handbook advises that, where possible, BCG vaccination for travellers should be given at least three months before arrival in a TB-endemic area.
Starting early also allows time for Mantoux testing if required and appropriate spacing of other live travel vaccines.
This can be particularly important for families travelling with young children and healthcare professionals preparing for overseas placements.
BCG vaccination assessment in Melbourne
People seeking BCG vaccination in Melbourne may require an individual assessment before vaccination.
This is particularly relevant for:
- healthcare workers travelling overseas
- people preparing for high-risk occupational placements
- families travelling with young children
- people with previous residence in high-TB-incidence countries
- people with uncertain previous BCG or TB history
A BCG vaccination clinic can assess vaccination history, potential previous TB exposure, the need for Mantoux testing and whether vaccination is appropriate.
For information about a Melbourne BCG vaccination service and online booking, visit the BCG Vaccination Melbourne listing.
https://www.iseegp.com.au/listing/bcg-vaccination-melbourne-bcg-vaccine-clinic-book-online/
The bottom line
BCG vaccination should not be treated as an automatic travel vaccine.
The first question is whether the person actually needs it.
The second is whether there is evidence of previous TB exposure or another reason vaccination may not be appropriate.
For selected people, this means a clinical assessment and sometimes a Mantoux test before vaccination.
Planning ahead is particularly important for healthcare workers and families travelling to countries with a high incidence of tuberculosis.
References
Australian Government Department of Health, Disability and Ageing. Vaccination for international travellers.
Australian Government Department of Health, Disability and Ageing. BCG vaccine.
World Health Organization. BCG vaccines: WHO position paper. Weekly Epidemiological Record. 2018.