Looking to ramp up supplies ahead of the opening of Covid-19 vaccination to all citizens over 18 years of age, the government has approved a payment of about Rs 4,500 crore as advance to vaccine makers like Serum Institute of India (SII) and Bharat Biotech against future supplies, sources said. SII will supply 200 million doses and Bharat Biotech is to supply another 90 million doses to the government by July at a pre-agreed rate of Rs 150 per dose. Sources said the finance ministry has relaxed rules to allow advance payment without bank guarantee to help the vaccine makers ramp up production. SII will get Rs 3,000 crore in advance and Bharat Biotech about Rs 1,500 crore. Earlier this month, SII CEO Adar Poonawalla had said that the company would require around Rs 3,000 crore to ramp up production capacity for making vaccines for COVID-19. Meanwhile, the government on Monday allowed citizens over the age of 18 years to receive Covid-19 vaccination from May 1 as it seeks to control the rapid spread of the virus. Under the third phase of its vaccination strategy, manufacturers will be required to supply 50 per cent of their monthly doses to the government and the rest to state governments or the open market. Vaccination will continue as before in the government of India vaccination centres free of cost for the eligible population -- healthcare and frontline workers and all people above 45 years of age. Latest data showed that over 2.59 lakh coronavirus infections pushed overall cases in India to more than 1.53 crore, making the country the second-worst affected nation after the US, which has reported more than 3.1 crore infections. India's deaths from COVID-19 rose by a record 1,761 to over 1.8 lakh.