A big part of the effort to halt COVID-19 in South Africa came to a halt overnight after the country suspended use of the AstraZeneca vaccine. Their data showed that the vaccine may only be as little as 10% effective against the South Africa variant, which Reuters notes is statistically insignificant. The biggest problem is AstraZeneca’s clinical trials, and it’s not the first time that issue has arisen:

South Africa will suspend use of the coronavirus vaccine being developed by Oxford University and AstraZeneca after researchers found it provided “minimal protection” against mild to moderate coronavirus infections caused by the new variant first detected in that country.

Health Minister Zweli Mkhize said Sunday that the rollout will be paused while scientists assess the data and determine a way forward. Officials had been eager to begin vaccinating health-care workers with the shots after 1 million doses arrived last week.

The data, disclosed at a news conference Sunday, showed that once the variant became dominant in the country in November, the vaccine provided no significant protection against illness — although all the cases of disease were mild or moderate. There were 19 cases of covid-19 caused by the variant among people who received the vaccine and 20 cases among people who got a placebo. That suggests the vaccine was 10 percent effective, but the difference could have been due to chance.

The AstraZeneca vaccine doesn’t appear to be effective against mild or moderate infections of the variant, but does it prevent more serious cases? No one’s sure, because their sample didn’t include older patients that are more likely to develop serious acute cases. That leaves them unable to tell whether there’s any point at all in using the AstraZeneca vaccine in regions where this variant dominates, especially with other vaccines reporting much better response against this variant. Even Johnson & Johnson’s relatively disappointing result of ~55% effectiveness against the variant still qualifies as epidemiologically effective, especially since that vaccine does appear to limit acute cases to milder levels and prevent hospitalizations.

So what next for AstraZeneca? They might need to redo their clinical trials with a better age spread in its sample, for one thing. And that might end up delaying the US’ approval of their emergency-use authorization, especially now that Johnson & Johnson applied for their own EUA on Friday. Any delay will take tens of millions of expected doses off the table for the US, although Johnson & Johnson’s expected approval will add 100 million in its first tranche. Even so, the FDA will think twice about using a vaccine that has no benefit against an already-extant variant, even one that got lots of funding in Operation Warp Speed.

The biggest blow will be for underdeveloped countries that hoped to benefit from the cheaper and easier-to-distribute AstraZeneca vaccine. Any delay or lack of effectiveness will put a big dent in plans to vaccinate the entire world in a short period of time, and may put additional pressure on Western nations to give up some supplies of other vaccine types.