AIIMS Director (Delhi) Dr Randeep Guleria reacted on the availability of the Pfizer's COVID-19 vaccine and other vaccines in India and availability of their doses in the country. He said that the data released by the company is very encouraging but it should be looked very carefully. "Whatever vaccines they are making have potential of giving immunogenicity and protection as far as COVID-19 is concern," he said. "The challenge with the vaccines is that, how long the immunity lasts and how much protective value that it gives as far as individuals are concerns," Dr Guleria added. "He said that other challenge with the Pfizer vaccine is that the vaccine should be kept at a very low temperature which is not practical for rural parts of the country and tough to maintain the cold chain," he further said.