The spread of the Delta variant, along with increased social mobility and the inconsistent use of proven public health measures, is driving an increase in both case numbers and deaths, he said at the 8th meeting of the International Health Regulations Emergency Committee on Wednesday.
"And after 10 weeks of declines, deaths are increasing again. The virus continues to evolve, resulting in more transmissible variants. Unfortunately, we are now in the early stages of a third wave," Ghebreyesus said.
"The Delta variant is now in more than 111 countries and we expect it to soon be the dominant Covid-19 strain circulating worldwide, if it isn't already," he added.
At the same time, there is "shocking disparity" in the global distribution of vaccines, and unequal access to life-saving tools, he lamented. Many countries still have not received any vaccines, and most have not received enough.
Covax, the international vaccine-sharing initiative -- led by the WHO) and other international organisations -- has shipped just over 100 million doses, so far.
Ghebreyesus stated that inequity has created a two-track pandemic -- namely, one track for countries with the greatest access to vaccines, who are lifting restrictions and reopening their societies, and a second track for those without vaccine access who are left "at the mercy of the virus".
He reiterated WHO's appeal for a massive push to vaccinate at least 10 per cent of the population of every country by September, at least 40 percent by the end of 2021, and at least 70 per cent by mid-2022.
Emphasising that vaccines alone will not stop the pandemic, he also called upon countries to persist with a "tailored and consistent approach". This includes using the full array of public health and social measures, and a comprehensive risk management approach to mass gatherings.
"So many countries around the world have shown that this virus can be stopped and contained with these measures," he stressed.
The global health agency is also reviewing options to digitalise the International Certificate for Vaccination and Prophylaxis, to support a harmonised approach for recording vaccination status.