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A lot of BCG vaccine doses are wasted in field areas because in a session only 3-4 children come for BCG vaccination, but the ampoule contains 20 doses. In this context, I seek the following clarifications:
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After dissolving (re-constituting) BCG vaccine, what is the safe duration during which time it should be used?
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After dissolving the vaccine, can it be preserved in remote areas where there is no cold chain except vaccine carrier (which multi purpose worker gets from distribution center) inside which frozen ice packs are there for 24-48 hours.
T.N. Chaturvedi,
Shahdol, Madhya Pradesh,
India.
Freeze drying process (lyophilization) has revolutionized the logistic of BCG vaccination. During the days of liquid BCG vaccine, there were several difficulties. The mycobacteria of BCG had a tendency to become non-viable fairly fast. Therefore, after a batch of BCG vaccine was produced, it had to be released quickly, often even before all the quality checks were completed. I was given to understand that an overage of organisms was sometimes put in so that no batch would fail the potency test. Such vaccine had to be used up within 2 weeks of release. It tended to produce larger scars than today's freeze dried BCG.
By freeze drying, better standardization and longer shelf life were achieved. Its potency is adjusted to what is essential and no overage is necessary. After a batch is manufactured, it could be kept until all quality tests are comp-leted before release. It has a long shelf life when kept refrigerated. It has better heat stabi-lity; the organisms remain viable for several weeks even at room temperature. A short exposure to even 38°C does not damage it.
Once reconstituted, the freeze dried vaccine is converted to liquid vaccine. But the potency is so titrated that its shelf life in the reconstituted liquid stage is far less than two weeks of the original version of liquid BCG. The general dictum is to use reconstituted BCG as soon as possible, but certainly within the same working day, allowing for a few hours only. The IAP Guidebook on Immunization stipulates that reconstituted BCG should be used up within 4 hours or a maximum of 6 hours. It is imperative that the liquefied vaccine must be kept cool. Both freeze dried and liquid vaccines should not be exposed to bright light.
Thus, the answers to Dr. Chaturvedi's questions are that 4 hours is a safe duration to use BCG after reconstitution and it should not be kept for more than one working day (6 hours maximum) under any circumstances.
T. Jacob John,
Emeritus Medical Scientist (ICMR),
439, Civil Supplies Godown Lane,
Kamalakshipuram,
Vellore 632 002, Tamil Nadu,
India.
E-mail: tjjohn @md4.vsnl.net.in
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