It was perhaps a human error that led to the death of four children after administration of measles vaccine last week in southern India, an inquiry team has concluded.
The federal Health Ministry team said the children died of severe brain hemorrhaged resulting from an anaphylactic shock, a systemic allergic reaction, highly rare, occurring in, say, one out of every ten lakh cases.
With the cold chain system also having remained in tact, the only conclusion possible was some human error had led to the tragedy. Possibly the vaccine became contaminated when kept in the open after dilution or something went wrong in the dilution process itself.
Otherwise all necessary precautions had been taken in matters like using syringes, the officials told the Times of India.
The Central Drug Laboratory, meanwhile, started testing 20 samples of the vaccine from the same batch that killed the children - 10 each collected from the fatal site in Tiruvallur and those lying with Human Biologicals Institute in Hyderabad.
Worried about HBI's good manufacturing standards, the Health Ministry is now dispatching a three-member team to HBI on Tuesday to check the PSU's measles vaccine production unit.
"HBI is a pre-qualified WHO unit. However, we need to be sure that it is following good manufacturing standards set by WHO and the government of India. The team will inspect the vaccine production area, check raw materials being used and inspect its quality control measures," an official said.
He added, "This case is really intriguing. A single child can be sensitive to the vaccine and suffer from an anaphylactic shock. But how can it occur on three children, one after another, after being administered the vaccine from a single vial. On the other hand, records show that 230 doses of the same vaccine batch were used in the same primary health centre (PHC) that day, but no other deaths were recorded."
The fatal vaccine batch was manufactured in February 2008 with expiry date of January 2010. Out of about 2.5 lakh doses of vaccine manufactured, 1.45 lakh doses were supplied to Tamil Nadu, where the tragedy took place. The rest were sent to nine other states.
"Around 20,000 doses of the vaccine from the same batch were used between April 4-23 without a single death. Over 230 children were vaccinated across seven villages on April 23 but no serious adverse reaction was detected," the official added.
The Human Biologicals Institute meantime asserted there was no lapse in manufacturing standards. In a statement, it said, "The samples of vaccines were drawn by an independent agency, Institute of Preventive Medicine, Hyderabad and it in turn sent the samples to Government's Central Drug Laboratory, Kasauli for testing. It was only after independent testing by the CDL, the batch was released to the market by the manufacturer. This should rule out the scope of manufacturing related quality issues."
For its part, the government of Tamil Nadu is putting in place a slew of measures to tackle emergencies in the future.
Next Wednesday, when thousands of children across the state go for routine vaccination, life-saving drugs, adequate medical staff and ambulances will be available at all PHCs. Vaccination is done in the state on Wednesdays.
P. Padmanaban, Director of Public Health, told The Hindu that the focus would be more on post-vaccination and children would be asked to remain at the PHCs for at least an hour after the vaccination.
"This week there might be an element of fear, but we are taking all necessary steps to infuse confidence in the people," he added.
About one lakh children are immunised in the state every month in 1,400-odd PHCs, 270 hospitals, 163 urban health centres and thousands of interior health centres.