The country's medicine regulator has asked for more information from pharmaceutical company Janssen before making a decision to approve its Covid-19 vaccine.

The US, European Union and South Africa have temporarily halted the rollout of the company's Covid jab due to fears over rare blood clots, the BBC reported this week.

The US Centres for Disease Control and Prevention (CDC) and US Food and Drug Administration (FDA) are reviewing data involving six reported cases in the States of a rare and severe blood clot in people who had received the vaccine.

The agencies said the events of blood clots appeared to be extremely rare.

The New Zealand Government has an in-principle agreement with Janssen Pharmaceutica to purchase up to five million Covid-19 vaccines, which are likely to be a single-dose shot.

The Ministry of Health said that Medsafe issued a number of additional requests for data from Janssen, after receiving information from the FDA about the cases of blood clots.

Medsafe group manager Chris James said the medicines regulator expected to provide an update on the Janssen approval process in the next two to three weeks.

"This will allow us time to investigate the data we receive so that when we do make a decision, we can reassure the New Zealand public about the safety and efficacy of the vaccine.

"We continue to receive information from our regulatory colleagues, which includes the FDA in the US and Therapeutic Goods Administration in Australia, who are also assessing the Janssen vaccine.

"Medsafe has a robust system in place for evaluating the safety and quality of medicines and vaccines for use in New Zealand, and will continue to make decisions based on the most up-to-date information."