“There is hope,” Tedros Adhanom Ghebreyesus told a meeting of WHO executives gathered to examine the global response to the pandemic.
“We will need vaccines and there is hope that by the end of this year we may have a vaccine.”
There are currently nine experimental vaccines in the pipeline of the WHO-led Covax global vaccine facility, which aims to distribute two billion doses by the end of 2021.
Some 168 countries have so far joined the Covax programme, but China, the United States and Russia are not among them.
Mr Tedros urged countries to work together to fight the disease, saying the most important factor in finding a vaccine was “political commitment from our leaders especially in the equitable distribution of the vaccines”.
He said: “We need each other, we need solidarity and we need to use all the energy we have to fight the virus.”
Drug makers and public health bodies around the world are racing to develop a vaccine, seen as crucial to bringing the pandemic under control.
China is in talks with the WHO to have its locally-produced Covid-19 vaccines assessed by the global health body, as a step toward making them available for international use, a WHO official said.
Meanwhile, the EU health regulator has launched a real-time review of a vaccine developed by US drugmaker Pfizer and Germany's BioNTech, which it is hoped could speed up the approval process by allowing researchers to submit findings without waiting for studies to conclude.
Both companies entered final stage talks with Europe last month to supply the bloc with up to 300 million doses of their potential coronavirus vaccine.
That follows a similar announcement last week that approval for rival AstraZeneca's jab could also be sped up. AstraZeneca has already signed a deal for up to 400 million doses of its vaccine.
In Africa, there are currently 15 clinical vaccine trials underway. Five trials are taking place in South Africa, four in Egypt, plus a single trial each in Guinea-Bissau, Ghana, Uganda, Kenya, Zambia and Zimbabwe.
African nations have teamed up to combat the pandemic, with painful memories of millions of Africans dying in the decade it took for affordable HIV drugs to become available on the continent.
On Tuesday, GlaxoSmithKline (GSK) and Vir Biotechnology also announced that the trial of their potential coronavirus treatment will move on to phase three.
The Comet-Ice study is evaluating Vir-7831 for the early treatment of Covid-19 in patients who are at high risk of being taken to hospital.
The treatment is an antibody that was selected based on its ability to neutralise the virus. It is also thought to kill infected cells, provide a high barrier to resistance, and achieve high concentrations in the lungs.
Following encouraging results from earlier stages of the trial, the study will now expand globally to additional sites in North America, South America and Europe.
Additional reporting by agencies.