A research conducted in India’s Gorakhpur district came into the news recently due to its findings on SA-14-14-2, a Chinese vaccine for Japanese Encephalitis. Involving 266 children, the study discovered that the vaccine resulted in very low levels of the neutralizing antibody IgG at various time intervals after vaccination. It is important to note, however, that the research did not investigate T-cell immune responses or cell-mediated immune responses.
Findings of the Study
The study revealed that the vaccinated children underwent a decrease in seroprotection against the virus. Seroprotection refers to an antibody response that has the capacity to prevent infection, such as after a previous infection with a microorganism or vaccination. Nearly 98% of the children who were given the vaccine did not display any IgG antibodies to fight the virus. Similar outcomes were observed in a Bangladesh study where children received the same Chinese vaccine.
Comparison with Other Vaccines
In contrast, an experiment using an inactivated vaccine called Jenvac, developed by Bharat Biotech and NIV Pune, showed superior protection after two years even from a single dose. This vaccine has been approved as a single-dose vaccine. A November 2020 trial revealed that two doses of Jenvac resulted in more antibodies than two doses of the Chinese vaccine.
Understanding Japanese Encephalitis
Japanese Encephalitis (JE) is a viral infection capable of causing brain inflammation. The disease is caused by a flavivirus from the same family as dengue, yellow fever and West Nile viruses. JE also contributes significantly to Acute Encephalitis Syndrome (AES) in India.
Transmission and Treatment
JE spreads to humans via bites from infected Culex species mosquitoes. These mosquitoes primarily breed in large water bodies and rice fields which have abundant aquatic vegetation. As of now, there is no antiviral treatment available for patients with JE. The only available treatment is supportive care, aiming at relieving symptoms and stabilising the patient.
Prevention
Effective and safe JE vaccines are available that can prevent the disease. The Indian government’s Universal Immunisation Program also includes JE vaccination.
About Antibodies
An antibody is a protein which the body’s immune system produces upon detecting harmful substances called antigens. There are 5 types of heavy chain constant regions in antibodies (immunoglobulin). They are classified into IgG, IgM, IgA, IgD, and IgE based on these types. IgG is the main antibody found in blood and plays a crucial role in the biological defense system due to its superior ability to bind to bacteria and toxins. This is the only type that can traverse through the placenta, providing protection for newborns as they receive IgG from their mothers.
