(Reuters) – Here’s what you need to know about the coronavirus right now:

Global vaccine summit

British Prime Minister Boris Johnson hosts a global vaccine summit on Thursday, urging nations to pledge funding for vaccinations against infectious diseases to help the poorest countries tackle the coronavirus crisis.

Representatives of more than 50 countries, including 35 heads of state or government, will come together virtually in London to raise funds for the GAVI vaccine alliance, a public-private global health partnership.

Safe or silent carriers?

China said 300 symptomless carriers of the novel coronavirus in Wuhan, the epicentre of the pandemic, had not been found to be infectious, in a bid to reassure people as countries ease restrictions. But some experts say asymptomatic infections are common, presenting a huge challenge in the control of the disease.

The World Health Organization defines asymptomatic cases as those who do not show symptoms but have been confirmed infected through a lab test, noting that there are few reports of truly asymptomatic cases.

Five vaccine finalists

The Trump administration has selected five companies – Moderna Inc, AstraZeneca Plc, Pfizer Inc, Johnson & Johnson and Merck & Co Inc – as the most likely candidates to produce a vaccine for the coronavirus, the New York Times reported on Wednesday, citing senior officials.

The selected companies will get access to additional government funds, help in running clinical trials, and financial and logistical support, the newspaper reported.

‘Simplified’ Olympics

Tokyo Governor Yuriko Koike said on Thursday it may be necessary to a stage a “simplified” Olympics next year due to the impact of the COVID-19 outbreak and that organisers were already discussing possible changes.

The Yomiuri newspaper, citing government and organising committee sources, said having fewer spectators, making Polymerase chain reaction (PCR) tests mandatory for all spectators – in addition to athletes and staff – and limiting movement in and out of the athletes’ village were among the options Japan would discuss with the International Olympics Committee.