|ALLERGY AFTER BCG VACCINATION
|Kul Bhushan: Proceed 18th Natl TB & Chest Dis
Workers Conf, Bangalore, 1962, 286-89.
In view of the variable and low levels of post-vaccination allergy elicited in the Indian Mass BCG Campaign vaccinated
groups as observed by WHO and Indian BCG Assessment Teams, some
studies were carried out to investigate some of the factors considered
having influenced the levels of post-vaccination allergy. The
reasons were potency and storage of vaccine, techniques, interval
between vaccination and retesting and tuberculins used. Potency
of the vaccine: Madras vaccine was compared with Danish vaccine.
The retest done at 3 months with 1 TU RT 23 showed 11.8 mm induration
with Danish and 11.9 mm with the Madras vaccine. Test done after
one year with 20 TU induration was 18.3 mm for both the vaccines.
It is reasonable to assume that the vaccine produced at Madras
is as potent as Danish vaccine. Storage of vaccine: A comparison
of post-vaccination allergy in respect of storage of vaccine by
the ICMR Assessment Team and by Mass Campaign Teams was carried
out in five groups of villages in the neighbourhood places where
five BCG teams were working in Tamil Nadu. The non-reactors were
vaccinated randomly by vaccines stored by either team and with the
placebo III group as control. The retest done after 3 months showed
that in all the five groups combined the mean size of indurations
vaccinated with vaccine stored by Assessment Team were more in the
vaccine stored by Mass Campaign Team. The loss of potency was 0.7
mm per week in vaccine stored by Assessment Team and 1.5 mm per
week stored by Mass Campaign Team. Techniques: The above
study was extended to five more groups vaccinated and tested by
the Mass Campaign Team. Assessment Team also vaccinated separate
groups with the same vaccine and tested on the same day. Mean size
induration for groups combined was higher for assessment team but
not significant. So, the techniques do not seem to make much difference.
Interval between vaccination & retesting: Analysis of
data collected on post-vaccination allergy in the groups vaccinated
by the Mass Campaign Teams retesting according to intervals showed
that the mean size induration decreased with the increase in interval
between vaccination and retesting from 1-20 months. Thereafter,
it rose again. These results indicate a tendency for the allergy
after vaccination to wane with passage of time. The rise is presumably
due to super infection or difference in batches of vaccine. In the
third year (not included in this paper) greater proportion of people
had bigger reactions. Besides, tuberculin used for retesting is
also found to give differences in mean size induration. Tuberculin
5 TU RT 22 gave larger reactions than 1 TU RT 23 with tween, the
differences were above 3 mm.
It can be concluded that at present Madras vaccine
is satisfactorily potent, the post-vaccination allergy is influenced
by storage of vaccine, by interval between vaccination and retesting
and type of tuberculin used for eliciting the allergy. Technique
of testing, reading and vaccination may not influence the results.
Under Indian climatic conditions the liquid vaccine should not be
used for more than 2 weeks. There is a need for Freeze-Dried vaccine.
|KEY WORDS: POST-VACCINATION ALLERGY, LIQUID
BCG, FREEZE DIRED BCG, MASS BCG CAMPAIGN.