US experts warn new Covid variants and states reopening may lead to fourth wave

Cases could plateau at a point equivalent to summer 2020 peak, while vaccines have reached relatively few people

Public health experts encouraged Americans to continue social distancing and wearing masks at a potentially critical inflection point in the pandemic - one in which highly effective vaccines could provide relief, but fervor to reopen public life could unintentionally spread new Covid-19 variants.

The warnings come the same week Texas and Mississippi flung open the doors to normal social life in their states.