Lessons from a vaccine

Published : Aug 25, 2006 00:00 IST

A vaccine for Japanese encephalitis was used in an immunisation campaign without a `bridging study'.

THE year 2005 is the biggest blot on the Japanese encephalitis (JE) control programme in India. The year recorded the largest number of cases and deaths in the past five years, at an all time high, - 6,727 cases and 1,682 deaths. The incidence in Uttar Pradesh alone, true to its reputation as the worst health care provider in the country, accounted for as many as over 6,061 cases and about 1,500 deaths.

Widely prevalent in most of Asia, JE is a disease that affects the central nervous system and is caused by a single stranded RNA (ribonucleic acid) virus belonging to the flavivirus family. The virus thrives in domestic pigs and aquatic birds whose systems amplify it. It is transmitted by Culex mosquitoes with humans serving as incidental hosts in its life-cycle when infected through mosquito bites. Only one person in every 400 infections develops the disease, which indicates the enormity of the spread of the infection last year. The fatality rate is about 25 per cent, which is also borne out by the outbreak data. There is no cure for the disease but it can be prevented by immunisation with vaccine.

With intense political pressure on the Central government to act, not only from U.P. but also from other States, the Union Ministry of Health and Family Welfare decided to launch a campaign-mode immunisation drive in select districts of endemic States based on the epidemiological data of the last five years. Eleven high-risk districts, with a total immunisation target of nearly 12 million children aged one to 15 were thus identified. These included seven in U. P. (Gorakhpur, Deoria, Kushinagar, Maharajganj, Lakhimpur Kheri, Sidharth Nagar and Sant Kabir Nagar), two in Assam (Dibrugarh and Sibsagar), one in Karnataka (Bellary) and one in West Bengal (Burdwan).

The vaccine that has been in use in India, as in most parts of the world, is the inactivated mouse-brain-derived vaccine, notwithstanding its limited efficacy (80-90 per cent), known side-effects, multi-dose regimen and high production costs. There are other inactivated vaccines under development in India and elsewhere, including genetically engineered ones, but these are yet to undergo evaluation and clinical trials. It is somewhat ironic that while India has provided more leads to vaccine development than any other country, Indian scientists have not been able to come up with a good vaccine, pointed out T. Jacob John, the eminent virologist from Christian Medical College (CMC), Vellore.

Chinese scientists have, however, developed one attenuated live vaccine based on the virus strain SA-14-14-2 grown in baby hamster kidney cells. It has been in use in China since 1988. In recent years it has also been introduced in South Korea, Sri Lanka and Nepal. Just one dose of the vaccine has been found to provide the required immunity for at least five years and its efficacy is reported to be between 80 and 99 per cent even 12 to 15 months after vaccination, and over 98 per cent with two doses. Significantly, its cost is also low. The vaccine is manufactured by the Chengdu Institute of Biological Products, whose production of 50 million doses is about 50 per cent of the total global production of all JE vaccines.

Notwithstanding the legitimate concerns over its safety (being a live vaccine), including severe Adverse Events Following Immunisation (AEFI), immunisation of over 200 million children has seen no severe safety-related incident so far. In particular, a major safety and efficacy study carried out in Nepal has proved the vaccine's credential to be good. It must, however, be noted that the vaccine has not yet been approved by the World Health Organisation (WHO) for use in its JE control programmes worldwide. In particular, the baby hamster kidney cell line used for its production needs to be pre-qualified by the WHO, though it has granted the Chengdu Institute Good Manufacturing Practice (GMP) certification.

The mouse brain vaccine is manufactured in India at the Central Research Institute (CRI), Kasauli. Its capacity, however, is only two million doses, which can, at best, be doubled if the demand is placed sufficiently in advance. The main problem is that increasing the capacity does not involve a mere scale-up of chemicals; large numbers of mice are required (two mice for a single dose of the vaccine). Thus the CRI has never been able to meet the sudden rise in domestic demand during exigencies.

"Because of the lack of a long-term strategy and necessary support from the government, the CRI did not play the role it could have played," said Jacob John. In fact, in 2004, Andhra Pradesh and Tamil Nadu had to import the vaccine to meet their demands. As an aside, it is pertinent to note the irony that U.P. failed to utilise four lakh of the six lakh doses of the CRI vaccine that was supplied at short notice at the State's request for use in its routine immunisation programme in early 2006.

Worldwide production of the mouse-brain vaccine is insufficient to meet the global demand. Owing to this, officials say, the Ministry could not procure enough vaccine from the global market to meet the requirement for the planned campaign. In October 2005, a decision was taken to explore the possibility of importing the SA-14-14-2 vaccine from China. The ministry sought to use the services of PATH, an international non-governmental organisation (NGO) funded by the Melinda Gates Foundation that has been working with the WHO in JE immunisation programmes in different parts of Asia, including China. In India, it has worked in Andhra Pradesh since 2000. At the end of 2005, Union Health Minister Anbumani Ramadoss signed a memorandum of understanding with the Chengdu Institute for the requisite quantity of vaccine during his visit to China.

PATH's website states that it was its negotiations with the Institute that helped bring down the price of the Chinese vaccine for India. "One of the greatest accomplishments so far has been working with the vaccine manufacturer and the countries to better forecast demand for the vaccine and to negotiate prices that developing countries can afford," it said. According to Ministry officials, the price for a dose was brought down from about Rs.45 to about Rs.8. PATH sees the introduction of a major immunisation drive involving nearly 12 m children using the Chinese vaccine as "precedent-setting protection" and a major achievement in its efforts to promote the Chinese vaccine worldwide. According to the website, currently PATH is involved in "helping the manufacturer prepare data to pursue pre-qualification from the WHO so that it would be easier for other countries to import the vaccine." It also supports clinical trials (in the Philippines) to confirm that the vaccine can be given along with measles vaccine to infants so that it fits into existing national immunisation programmes.

In January, the Ministry ordered animal toxicity tests to be done by the National Institute of Nutrition (NIN), Hyderabad, on some vaccine samples. Based on the 28-day toxicology study data, the Drug Controller General of India (DCG-I) granted his approval in February for its introduction into the immunisation campaign. The order was placed for a total of 13.5 million doses from the Chengdu Institute in March. These were delivered in four lots between May and July. The immunisation campaign itself got under way on May 15, beginning with the seven U.P. districts, and all the 11 districts were covered in four phases (perhaps in accordance with the vaccine delivery schedule). Further, within the districts, it was conducted in two phases, first in rural and then urban areas.

But soon after the campaign got under way in U.P., the AEFI monitoring and referral system established under the State health machinery reported 219 AEFIs and eight deaths out of a total of 68,18,596 children immunised. AEFI data are collected within a few days (typically 48 hours to a week) of post-vaccination. A Central team investigated these cases and submitted a report.

According to the report, the AEFIs included fever, at times accompanied by vomiting, and acute hypersensitivity reactions such as rashes, respiratory distress, sweating, headache, vertigo and convulsions. As regards the eight deaths reported by Baba Raghav Das (BRD) Medical College, Gorakhpur, the report stated that vaccine-linked proximal causes could be attributed to six of these, with one categorised as `probable', two as `possible' and three as `unlikely'.

An expert group constituted under the Director-General of Health Services (DGHS) reviewed the report and recommended postponement of the immunisation drive in new places until the causes of the deaths were fully established. However, an emergency meeting on June 23, chaired by Health Secretary P. K. Hota and attended by representatives of the Indian Council of Medical Research (ICMR), the DGHS, the WHO, PATH and the Health Ministry's immunisation division, decided against the suspension of the immunisation campaign. The argument was that such a move would have an adverse impact on the immunisation programme itself.

At the meeting, the ICMR Director-General expressed the need for a cautious approach ahead. According to the minutes of the meeting, he held the view that while the risk-to-benefit ratio could be appreciated, since some of the AEFIs seemed to be of serious nature, they needed to be investigated further. He also stated that the set-up for monitoring the AEFI and the referral system was poor. Commenting on the vaccine's safety, he said that unlike the mouse-brain vaccine, there was no benchmark for the Chinese vaccine-related AEFIs. The head of the Department of Paediatrics at Lady Hardinge Medical College called for an in-depth examination before starting the campaign in a new place.

The WHO representative opined that the association of adverse events with the vaccine was quite unlikely and, therefore, it would not be advisable to discontinue the campaign. The PATH representative also argued against suspension on the grounds that the adverse events were much less than the WHO standards for other live attenuated vaccines such as the one for measles. She argued that post-market surveillance would give a better insight into the AEFI at the field level. The opinions of the WHO and PATH prevailed and the group decided to continue with the immunisation.

Following the meeting's deliberations, however, a special group was constituted under Additional Director-General of Health Services Shiv Lal to review a set of tests and protocols of samples from Gorakhpur. It met the same day, and based on the advice of the Director-General, ICMR, recommended that sera and cerebro-spinal fluid (CSF) samples from the Gorakhpur AEFI cases be sent to the National Institute of Communicable Diseases (NICD), New Delhi, and the National Institute of Virology (NIV), Pune, for IgM-antibody tests, antigen detection tests, polymerase chain-reaction tests and sequence analyses and tissue culture inoculation tests. It also recommended IgE-antibody mediated allergen specific response tests at the Patel Chest Institute of Delhi University. From a total of 10,53,1554 children vaccinated, there were 504 cases of AEFI and 22 deaths reported.

The NICD and NIV tests were done on 17 CSF samples and two sera samples obtained from the BRD Medical College and five sera samples from the U.P. public health team. For some inexplicable reason, the IgE antibody tests, which would have thrown light on the allergic responses, were not done. The NIV/NICD tests seem to rule out the presence of the wild type JE virus or the vaccine JE virus. IgM and JE virus antibodies could not be detected in 14 of the 16 CSF samples (one CSF vial was apparently empty) and the two remaining showed very low reactivity with JE virus. Detailed PCR tests also did not reveal the presence of JE virus RNA. Also, the inoculation of samples into babyhamster kidney cells at the NIV, which are sensitive to the virus, did not show any amplification of the virus.

It is pertinent to point out, however, that these tests only show that the deaths have not been caused by the JE virus or the vaccine virus. The causes of death themselves are yet to be established. Yet another expert group has been constituted under Jacob John to study the case histories of the 22 death cases. "Given the expected death rates by age group by different hospitals, the number of deaths within a period of two weeks is not negligibly small," Jacob John said. "But no particular phenomena seem to stand out; there is no uniform set of symptoms in these deaths," he added. "There was one severe case of jaundice. In Assam, the death cases seem to be from a cluster of some viral encephalitis and therefore most unlikely to be related to the vaccine. Since initial information is based only on first information reports, we have asked for detailed case descriptions," he said.

It may well turn out that none of the deaths was caused by the administering of the vaccine. As Sobhan Sarkar, consultant to the immunisation division in the Ministry, pointed out, since the number immunised is large, the number of AEFI and deaths seem high even though they are far lower than internationally accepted limits. "The tests have clearly ruled out any vaccine-related safety issue," Sarkar stressed. "We are also doing post-marketing surveillance using a captive population in Bellary and Burdwan with a sample size of 720 in each," he added. Asked about the need for animal toxicity studies when clinical data are not generated, Sarkar said that the Chinese toxicity data were not good. "These did not show any neurotoxicity and, taking into the global efficacy and effectiveness data, it was under the ICMR's recommendation that the government has gone ahead," Sarkar asserted.

The incidents have, however, raised the issue of non-adherence to procedural norms when introducing a new vaccine. The Chinese vaccine may have been rushed through without carrying out the prescribed `bridging study' on safety and efficacy in the Indian context, the Ministry's noble intentions notwithstanding.

"It was a difficult decision to take," says N.K. Ganguly, the ICMR Director-General. "Last year there were so many deaths. So it was not a normal situation. One of the parameters that we looked at was the background data. We looked at AEFIs elsewhere within the limit of the desired risk-benefit ratio. So we exercised abundant caution and carried out certain toxicology studies. An intra-cerebral injection of the vaccine was given to mice, which did not die. We ordered tests on viremia, mosquito surveillance, tests to show that really good antibodies developed and ensured that monitoring of AEFIs and referral and advance reaction systems were put in place," he added.

But experts point out that the percentage of respiratory distress in the AEFI can vary from population to population and such clinical studies should have preceded the immunisation campaign. The present data shows that 5-6 per cent had this syndrome and if the population is susceptible to asthmatic allergies, this kind of AEFI can become very serious, they point out.

"Clinical evaluation is not possible with neurotoxicity studies," said Jacob John, who had approved licensing the import of Chinese vaccine into India based on available data, assuming that bridging studies would be done. "In some sense it is unethical. The dynamics of the response to the vaccine should be studied in the Indian context, where nutritional status is compromised and JE infection can coexist with many other infections. Doing animal toxicity studies is like Caesar's wife appearing to be honest. It is not sufficient to do something for the sake of it. The vaccine should be proven to be safe," he added.

It appears that the ICMR does not seem to have been involved in the original decision to use the Chinese vaccine in an immunisation campaign. "Normally the dossier on any new vaccine goes through the ICMR. This time it does not seem to have followed that route," said Jacob John. In fact, being a live vaccine it should have got the approval of the Genetic Engineering Approval Committee (GEAC) of the Ministry of Environment, a view that the GEAC had expressed in its February meeting.

It was "not rushed through at all", avers Hota, Ministry of Health and Family Welfare Secretary. "We have exercised all diligence in the matter and have used the experiences of China, Korea and Nepal. We have had discussions with the WHO and PATH." Asked about the DGCI clearance without an appropriate bridging study, Hota said that emergency needs and exigencies were taken into consideration and the regulations allowed for that. "I am satisfied that we have benefited the children of the country."

"Given that the WHO is yet to approve the vaccine for its programmes, its certification of safety and efficacy based on available data is testimonial; it is not the same thing as evaluation. So our own limited small-sample studies using a cohort population of 15-20,000 is necessary," Jacob John pointed out. The issues do not seem to have been thought through. For instance, careful population antibody studies should have been carried out to collect baseline data. Without that, in spite of the large cohort of 11 lakh children, the vaccine's efficacy cannot be determined. In fact, such a study would have shown whether an immunisation campaign was necessary at all after last year's widespread infection, which would have conferred a baseline natural immunity to the population. In fact, this is the reason why JE occurs in cycles of two to three years.

So, why was the campaign launched in such haste? "It is a like a jigsaw puzzle with all the pieces falling in place all by themselves," said Jacob John. "There was all-round pressure on the government after last year's deaths to do something. The government was well meaning when it was looking for a vaccine. PATH came in to help locate the source. The Chinese vaccine was suddenly available and that too at low cost. The vaccine had good credentials and it was blessed by the WHO. So everything seemed to fit in just in time to launch a campaign before the disease's onset season. Unfortunately science was not applied."

"There is no pattern in the manner in which the government approaches health issues," said Jacob John. "It differs from crisis to crisis. This is because of a lack of a system that looks at public health constantly... . A professional body [is needed] that is in constant two-way interaction with the health services to look at data, study the epidemiological patterns, forecast needs and act as an advisory body to take appropriate steps in advance. Without such a structure all you get is knee-jerk reactions and you look to external agencies for advice. The entire health care system has to change."

Indeed, the role of PATH in this particular case has come in for criticism among medical scientists. They question the manner in which the government seems to have reposed faith in such organisations, ignoring the views of Indian medical research community. PATH itself has claimed that it was involved in microplanning the immunisation schedule, providing technical support to the campaign, and carrying out post-market surveillance. However, according to Sarkar, PATH was engaged only to provide "technical support" based on its experiences elsewhere. "Microplanning was done entirely by us," he asserted.

Scientists have also questioned the manner in which a live RNA virus vaccine has been introduced without adequate clinical tests. The following are their main concerns: First, RNA viruses are notorious for reassortment; the vaccine virus could reassort in combination with other RNA viruses in either the host system or in the environment. Second, the reversal from attenuated state to a virulent state. In this context, it is pertinent to note that SA-14-14-2 has been the only strain in which attenuation has been possible. So, being a live virus, it may well become unstable and virulent. Though the Global Advisory Committee on Vaccine Safety (GACVS) has opined that since SA-14-14-2 vaccine is based on 57 nucleotide changes and 27 amino acid substitutions, reversion to virulence is unlikely, apprehension on this count will always remain.

So, in the ultimate analysis, even if the vaccine has been able to prevent an outbreak of the disease this year, the episode has brought to focus the importance of applying science-based procedures when introducing any new drug or vaccine. In fact, without these, it would seem hard to establish scientifically the efficacy and safety of the Chinese vaccine in the Indian context and there would be no scientific basis to use it in another campaign or as part of the national immunisation programme.

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