BCG vaccine for long term protection, yes or no? — Boo Soon Yew

SEPTEMBER 19 — I write in sad response to the predicament of the family that is mourning the loss of their 19-year-old girl due to tuberculosis and indeed my sincere condolences to them. Yet at the same time I also write in disagreement to a very misleading headline in a local English daily that mentioned “BCG won’t prevent TB in adults”.

The said article starts with an opening paragraph stating “...BCG (Bacillus Calmette-Guerin) vaccination — will not stop you from being infected with tuberculosis (TB) as adult.” says a lung specialist in paragraph 2, who chose to be anonymous as mentioned further down that article.

To me, as a teacher of Biology, one who has been a medical student before, this is an utterly irresponsible statement to make (unless of course it was misquoted by the reporters concerned).

How can one make a statement that BCG will NOT STOP YOU from getting TB as an adult when it has been proven otherwise for millions of people who have enjoyed its protection since its inception from the admirable efforts of Albert Calmette and Camille Guerin in France, carrying out their research from 1905 to 1918 on animals.

In the end a weakened antigen was chosen, sub-cultured 230 times, and was first used in 1921 on a child in Paris.

In Malaysia, it is given at birth and at 12 years old, a norm which many schoolchildren will recall fondly or otherwise when the nurses make a visit to the school and all students make a bee-line to them in the hall, with an intradermal injection of the BCG vaccine as a “souvenir”. However, this policy was changed to just once only at birth from 2001. 

Nevertheless, personally as a 52-year-old who had gone through the old double BCG vaccination in the past, and of course with the well-defined scar on my right shoulder, I can safely attest (as many other adults in Malaysia) that we have certainly enjoyed the protection from BCG well into our adult years, 40 years in fact, and counting.

Doing a quick Google search on “BCG protection duration” yields at the top of the Search, an article from The Lancet, a very renowned medical journal, regarding a retrospective study done in Norway on individuals aged 12-50 years.

The researchers also assessed the long term vaccine effectiveness (VE) in these Norwegian-born individuals. Their findings were consistent with “long lasting BCG protection” but “waning of VE with time”.

The long lasting BCG protection part is pretty straightforward. The waning of VE or “Vaccine Effectiveness” will need some epidemiology explanation.

The numbers from the Norwegian study during a 40-year follow-up show tuberculosis episodes with a VE of 58 per cent in 10-19 years ranging to 42 per cent in 30-40 years.

Pulmonary tuberculosis show a VE of 63 per cent in 10-19 years ranging to 40 per cent in 30-40 years.

What these numbers mean are the percentage drop from the number of cases you would expect IF they had not been vaccinated.

The point is to acknowledge of course that there will be some who are vaccinated who can contract tuberculosis later in life. Yet it is also pertinent to point out that BCG vaccination DO PROTECT individuals well into adult life.

What is vital to consider now is how individuals who have been given BCG vaccination contract tuberculosis later in life. Are there any predisposing factors? Are there any prevailing socio-economic factors or even the environment where one lives in?

Hence coming back to that statement in that article I mentioned at the beginning, the good doctor should have phrased his statement as “BCG will not stop SOME from being infected with TB”.

May our own researchers in Malaysia seek to offer some answers based on their Malaysian clinical experience in the hope that answers can be found to explain and take counter-measures for the future to battle a once thought-to-be-vanquished foe, the Mycobacterium bacillus bacteria.

* This is the personal opinion of the writer(s) or publication and does not necessarily represent the views of Malay Mail.

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