Prime Minister Narendra Modi on Friday said that he had an “excellent discussion” with his United Kingdom counterpart Boris Johnson on the ties between both countries in the next decade. A press release by Modi’s office said both the leaders reviewed the “promising cooperation” between India and the UK in coronavirus vaccine development and manufacturing.

“We agreed to work towards a quantum leap in our cooperation in all areas trade and investment, defence and security, climate change, and fighting Covid-19,” Modi tweeted.

A coronavirus vaccine developed by drug manufacturer AstraZeneca and the University of Oxford is seen as offering one of the best hopes for many developing countries because of its cheaper price and ability to be transported and stored at normal temperatures. Drug manufacturer Serum Institute of India in Pune has partnered with AstraZeneca and Oxford University to produce the Covishield vaccine in the country.

The UK government, which has secured 100 million doses of the vaccine, has targeted the rollout to begin before Christmas next month. However, doubts that have been raised about the vaccine after AstraZeneca and Oxford University acknowledged a manufacturing error.

Based on the strength at which the doses were given, the vaccine appeared to be either 90% or 62% effective. The average efficacy, the developers said, was 70% in phase three trials. But questions mounted on why there was there such a large variation in the effectiveness of the vaccine at different doses, and on why a smaller dose appear to produce much better results.

On Thursday, the British government’s Chief Scientific Adviser Patrick Vallance said that the main point about the AstraZeneca vaccine against the coronavirus was that it was effective, reported Reuters. “The headline result is the vaccine works and that’s very exciting,” Vallance said at a news conference with Prime Minister Boris Johnson.

Chief Medical Adviser Chris Whitty, answering a question about the doubts raised, said there was always scientific debate about virtually everything. The same day, Serum Institute of India also said that the vaccine being is “safe and effective”, and that the Indian trials are progressing smoothly with strict adherence to all protocols. Modi is scheduled to visit the Pune-based firm on Saturday to review the vaccine development work.