NEW DELHI: With a long road ahead for vaccines and drugs, scientists are now exploring age-old technique of passive antibody therapy as potential treatment for COVID-19, which has infected over 5 lakh people across the world and killed at least 24,000.

Antibodies are protein molecules released by the body when a foreign substance (like for instance, virus) enters the system. These molecules bind to the foreign substance and neutralize it. Simply put, they are the weapon used by the immune system to fight new infections.

In case of COVID-19, over 1.22 lakh people, including a large young population, infected with the disease have recovered globally. Now, some molecular laboratories and diagnostic companies in countries worst hit by the pandemic -- China and US-- are racing to develop effective tests which can detect and assess these antibodies in the blood of patients who have recovered from the illness and also analyse if the antibody laden plasma of these recovered persons can be infused in patients at early stage of the disease.

It is an age-old technique, a classical way of dealing with infections being used since early 19th century. When a patient is at an early stage of infection, he makes antibody after 5-7 days, but by then he/she gets sicker and its becomes difficult to fight the infection. Basically, your natural antibodies are coming too late to protect you. In this technique, antibody-laden serum from a previously recovered patient can be infused in a patient at an early stage, to prevent the progression of the disease," explains noted virologist T. Jacob John, who retired as Professor of virology from Christian Medical College (CMC), Vellore.

The data is scarce and inconsistent about how effective the technique is against COVID-19 and concerns over any immunological reaction. Some clinical trials are underway, but it is too early to speak about its accuracy, experts said, but added that it may have potential".

While it is too early for India to experiment the approach, scientists in the country are looking at experiments with hope.

Such approach can be tested when the number of infections is very high, like for instance in China or US (where it has crossed 80,000). We are also looking at it, but currently we are not at the stage, where we have sufficient number of people who have recovered from this catastrophic illness. But clearly that is an area which is being keenly observed," said noted scientist Dr Anurag Aggarwal who heads the CSIR- Institute of Genomics and Integrative Biology (IGIB), Delhi.

As on Friday, India recorded as many as 724 cases of COVID-19, out of which around 67 have recovered.

The US Food and Drug Administration (FDA) has already classified it as an investigational new drug under an emergency approval system and clinical trials have begun. China too has been experimenting with the approach since early days of the outbreak, with modest success.

New York has announced its plan to use the therapy as part of its strategy to fight COVID-19 last week. If it succeeds, it may use it for their front-line health workers who may have been exposed to the virus.

A general principle of passive antibody therapy is that it is more effective when used for prophylaxis than for treatment of disease. When used for therapy, antibody is most effective when administered shortly after the onset of symptoms," says the study published in the Journal of Clinical Medicine.

The intervention was also adopted during the 1918 HINI influenza outbreak. A large case study conducted on 1,700 patients who received blood serum from survivors showed low mortality. It also showed some modest results in the 20092010 H1N1 influenza virus. Its efficacy for the new coronavirus remains under investigation.

So far there have been no approved drug or vaccines for COVID-19.

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Can antibody therapy help fight COVID-19? - Livemint