MUMBAI, India (AFP) — The head of the world’s largest vaccine maker directly tweeted US President Joe Biden on Friday urging him to lift an export ban on raw materials desperately needed to make more coronavirus shots. The unusual step by Serum Institute (SII) chief Adar Poonawalla underlined the crisis in providing vaccines to developing nations, many of which rely heavily on the firm for supplies. “Respected @POTUS, if we are to truly unite […]