Are human challenge studies effective? (GS Paper 3, Science and Technology)
Why in news?
- Recently, the ICMR Bioethics Unit posted the consensus policy statement for the ethical conduct of controlled human infection studies (CHIS), also known as human challenge studies, in India.
- The consensus policy statement has been posted on the Indian Council of Medical Research (ICMR) website.
Why is India venturing into undertaking human challenge studies?
- Human challenge studies, in which human beings are exposed to diseases to learn more about it, have been carried out for hundreds of years; the yellow fever study in the early 1900s, for instance, established that mosquitoes transmitted the yellow fever virus. However, India has not undertaken such trials before.
- Human challenge studies are almost always conducted to understand the various facets of infectious microbes and the diseases or conditions caused by such pathogens. The disease burden and mortality from infectious diseases is significantly high at around 30% in India.
- Though traditional human clinical trials have been carried out in the country for a very long time, the inclusion of human challenge studies will help supplement traditional clinical studies and speed up the process of finding safe and effective interventions in the form of drugs and/or vaccines.
- The human challenge studies will vastly help in providing better insight into multiple aspects of even well-studied pathogens, infection, transmission, disease pathogenesis and prevention. Since many infectious diseases are endemic in several developing countries, and resistance to existing drugs is increasing, there is a pressing need to find more effective medical interventions.
What is the fundamental difference?
- The fundamental difference between the two scientific methods is the nature of exposure to pathogens by participants.
- While participants in traditional clinical trials are strongly advised to adopt and adhere to safety measures to avoid getting infected and infection is left to chance, the opposite is the case with human challenge studies. Volunteers in a human challenge study are deliberately exposed to disease-causing pathogens.
- The second major difference is that traditional clinical trials are undertaken to study the safety and efficacy of drugs and vaccines, whereas human challenge studies are carried out to understand the various facets of infection and disease pathogenesis besides selecting the best candidate drug or vaccine.
- The third difference is that while the adverse effects of the candidate drugs or vaccines are not known in both the studies (safety is evaluated for the first time in humans during the phase-1 stage of a traditional trial), volunteers in a human challenge trial face an additional risk when deliberately exposed to the pathogen.
- Finally, human challenge studies are often undertaken to study “less deadly diseases” such as influenza, dengue, typhoid, cholera and malaria, unlike in traditional clinical studies.
What special safeguards are followed?
- Except in very rare cases, as in the SARS-CoV-2 virus that causes COVID-19, the infectious agents that are tested in human challenge studies are well-known and studied.
- To reduce harm to the participants, a weaker or less virulent form of the pathogen is used. The other important requirement is the availability of a ‘rescue remedy’ to prevent the disease from progressing to its severe form.
- An exception was the reliance on remdesivir as a rescue remedy for participants in the studies involving SARS-CoV-2 virus even when the substantial mortality benefit of remdesivir was not known.
What makes human challenge studies ethically more challenging?
- That participants in a human challenge trial are deliberately exposed to a disease-causing pathogen makes it ethically more challenging.
- The ICMR consensus statement has clearly mentioned that only healthy individuals in the 18-45 years age bracket are to be enrolled. Children and women who are pregnant, lactating or planning to conceive within the study period will not be enrolled; children will be included when “deemed appropriate”.
- Participants with pre-existing medical conditions are to be excluded but very often people are unaware of many medical conditions. This makes it essential to carry out detailed medical examination of the participants before enrolment.
- It remains to be seen how “informed” will be the informed consent, especially when the pathogen is studied in specific age groups such as children or disadvantaged groups, given the riskier nature of human challenge trials and the compulsion to get people enrolled in the new research methodology.
- The HPV vaccine trial in 2010 became notorious as informed consent requirements were flagrantly violated, as also during the Covaxin trial in Bhopal in 2020-2021.
Turbulence hits UDAN scheme, 50% routes grounded
(GS Paper 2, Health)
Why in news?
- The government’s biggest claim to success in aviation since 2014 is building “74 airports in seven years”, as opposed to the same number built in the seven decades since Independence.
- However, only 11 of these airports have actually been built from scratch, while 15 airports have fallen into disuse over this period, due to the collapse of almost half the routes launched under the regional connectivity scheme (RCS).
- This largely involved the revival of old airstrips that were either lying unused or were used sparsely. The government launched 479 routes to revive these airports, out of which 225 have since ceased operations.
Greenfield airports:
- Only 11 greenfield airports have become operational since May 2014.
- These are the airports at Mopa in Goa, Shirdi and Sindhudurg in Maharashtra, Kalaburagi and Shivamogga in Karnataka, Kushinagar in Uttar Pradesh, Orvakal (Kurnool) in Andhra Pradesh, Durgapur in West Bengal, Pakyong in Sikkim, Kannur in Kerala, and Donyi Polo in Arunachal Pradesh.
Waterdomes:
- The figure of 74 new airports, includes nine heliports and two waterdromes.
- These two waterdromes, built for seaplanes between Gujarat’s Gandhinagar and the Statue of Unity in Kevadia, closed down soon after the Prime Minister launched them in October 2020, as SpiceJet discontinued its flights after a “change in technical requirements”.
- As many as 15 airports, including Sikkim’s only airport in Pakyong, and those in Punjab’s Adampur, Pathankot, and Ludhiana do not see any flights any more.
About RCS:
- The RCS, also known as the UdeDeshKaAamNagrik (UDAN) scheme, was launched with the aim of taking flying to the masses by improving air connectivity for Tier-2 and -3 cities, and subsidising air travel on these routes.
- The routes are awarded after a bidding process, and the winning airlines are given certain incentives, along with viability gap funding (or a subsidy) equivalent to 50% of the seating capacity on their aircraft. In return, the airlines sell 50% of their seats at a flat rate of ₹2,500 per hour of flight, in order to make air travel affordable.
- The cost of the subsidy is borne by Indian airlines flying on non-RCS routes, who pay an RCS levy of ₹15,000 per departure, as per the latest revision that came into effect in April 2023.
- The airlines further pass the levy on their passengers on non-RCS flights. A total sum of ₹2,038 crore has been collected as RCS levy. The scheme also set aside a sum of ₹4,500 crore to revive old airports by recarpeting runways and erecting terminal buildings.
- Of these, 46 airports have been redeveloped by the Airports Authority of India (AAI), and the remaining by State governments and public sector units (PSUs).
- The government has so far spent ₹3,490 crore on these airports. The Union Finance Ministry approved another ₹1,000 crore for this purpose in May 2023, for a period of three years.
Commercially unviable:
- Of the 225 routes that have ceased operations, 128 routes shut down even before completing the mandatory three-year period under the scheme.
- Airlines found 70 of these routes to be commercially unviable despite the subsidy, while the remaining 58 have been cancelled due to “non-compliance” by the airline operator or the airline surrendering routes, or the airline companies shutting down.
- The objective of the scheme was that after the three-year period, airlines would be able to sustain operations on their own without government support, but out of the 155 routes that have completed three years, only 58 have survived.
Plastic pollution widespread in water bodies across the world
(GS Paper 3, Science and Technology)
Why in news?
- Two papers recently found evidence for widespread plastic contamination of coral reefs and freshwater lakes.
- The reef study finds that larger fragments (mostly debris from the fishing industry) make up most of the plastic found, and these macroplastics are especially abundant in deep reefs.
- The assessment of freshwater lakes and reservoirs reveals that all assessed bodies of water were contaminated with microplastics.
Key Findings:
Contamination of reefs:
- Researchers surveyed global reefs for macroplastics (over 5 cm) and other debris in 84 shallow (less than 30 metres deep) and deep (30-150 metres) coral ecosystems at 25 locations across the Pacific, Atlantic and Indian Ocean basins.
- Macroplastics accounted for 88% of the debris found. Levels of macroplastics were highest in the deep reefs.
- In most surveyed areas, fishing vessels were identified as the main source of plastic, such as lines and discarded traps.
- The findings contrast with the global pattern observed in other nearshore marine ecosystems, where macroplastic densities decrease with depth and are dominated by consumer items.
Contamination of fresh waters:
- They sampled the surface waters of 38 lakes and reservoirs in 23 countries mainly concentrated in the Northern Hemisphere. They found microplastics (over 250 microns) in all sample sites.
- Two types of lakes are particularly vulnerable to plastic contamination: lakes and reservoirs in densely populated and urbanised areas and large lakes and reservoirs with elevated deposition areas and high levels of anthropogenic influence.
- They found plastic concentrations varying widely among lakes. In the most polluted lakes, plastic concentrations were found to “reach or even exceed those reported in the subtropical oceanic gyres, marine areas collecting large amounts of debris”.
Way Forward:
- The two studies demonstrate the widespread contamination of water bodies with plastic debris, and underscore the urgent need for coordinated, systematic monitoring of plastic pollution.
