South Africa’s health regulator has approved the Johnson & Johnson’s COVID-19 vaccine, paving the way for large-scale deliveries government has put at the heart of its immunisation plans.

The conditional approval by the South African Health Products Regulatory Authority (SAHPRA) comes less than four months after it started a “rolling review” of the J&J vaccine, which has been administered to healthcare workers since mid-February in a research study.

J&J aims to supply the country with 31 million doses of its single-dose vaccine, with 2.8 million doses being made available in the second quarter, it said in a statement announcing the approval.

SAHPRA said in a separate statement the vaccine’s registration on March 31 was a significant step in the fight against COVID-19. It said its authorisation was subject to conditions including that the vaccine is administered in line with the government’s immunisation plan and that periodic safety updates would be submitted.

The J&J shots will come from local pharmaceutical company Aspen, which will be manufacturing up to 300 million doses under licence.

South Africa’s vaccination campaign was dealt a blow in early February when it put on hold a plan to start inoculations with AstraZeneca’s vaccine, after a small trial showed it offered minimal protection against mild to moderate COVID-19 caused by the dominant local coronavirus variant.

The government then switched to using the J&J shot in an “implementation study” to start protecting frontline healthcare workers with limited doses. So far it has vaccinated roughly 260,000 people, out of 1.25 million health workers, health ministry data show.

The pace of vaccinations has been slow, with health experts, trade unions and businesses urging the government to ramp up vaccinations once more supplies become available.

The government is also expecting 20 million doses of COVID-19 vaccine from Pfizer, as well as supplies from the COVAX vaccine distribution scheme co-led by the World Health Organisation and partners including the Gavi vaccines alliance.

A large clinical trial of J&J’s vaccine, which was conducted in eight countries including South Africa, showed the vaccine was 66% effective in preventing moderate to severe COVID-19 infection and 85% effective in stopping severe disease and hospitalization.

Pfizer’s vaccine was 100% effective in preventing symptomatic cases among trial participants in South Africa, the company said on Thursday, adding, however, that the rate was derived from a group of 800 participants, a relatively small sample.