New Delhi, Aug 12 (IANS): Cautiously welcoming the news of Russia registering the world's first Covid-19 vaccine, Indian health experts on Tuesday stressed that it would be too early to say if it is safe or not as the vaccine was tested on very few volunteers.

The clinical trials of the vaccine started on June 18 and included 38 volunteers.

The volunteers were divided into two main groups - one group consisted of 18 people and the other group had 20.

Russia on Tuesday became the first country in the world to register a Covid-19 vaccine jointly developed by the Gamaleya Research Institute and the Russian Defence Ministry.

According to Dr Rajesh Chawla, Senior Consultant, Respiratory and Critical Care at Indraprastha Apollo Hospitals in New Delhi, very little is known about this vaccine as it claims to help people build immunity against this novel virus.

"It is very early to measure its efficacy and safety," he told IANS.

According to him, a lot of parameters like age, people with multiple co-morbidities, the possibility of allergic reactions and the likes will have to be monitored before the vaccine is mass-produced.

Speaking to IANS, Dr Praveen Gupta, Director and Head, Neurology at Fortis Memorial Research Institute at Gurugram, said: "The Russian vaccine based on an inanimate protein of adenovirus has been brought to market with very short term trials of very few volunteers".

As a medical principle, before any vaccination is used for large-scale public use, "it is advisable in view of safety and adequate prevention of a communicable disease that proper and long-duration trials are conducted before the clinical use of the vaccine," the doctor stressed.

The World Health Organization (WHO) has also raised concerns about the vaccine.

"It is too early to tell if it is safe or not. Maybe in two months, the efficacy of the vaccine will be determined," said Gupta.

According to Dr Jyoti Mutta, Senior Consultant, Microbiology at Sri Balaji Action Medical Institute in New Delhi, considering the pandemic and emergency-like situation all over the world, the Covid-19 vaccine from Russia has raised hopes.

"But safety and efficacy are important and we need to keep an eye on its upcoming results too," Mutta told IANS.

"Every vaccine needs to pass all necessary trials and stages, and the significant results of any vaccine are seen in a minimum of one year with mass users but considering the situation everyone seems to be in a rush. We should be hopeful but wise as well," she noted.