Oxford/AstraZeneca Fails to Prevent Mild to Moderate Covid-19 From B.1.351 (“South Africa”) Variant

The rise of variants of SARS-CoV with alterations at the key spike protein, notably the “South Africa” variant (B.1.351), has posed potential challenges to the covid-19 vaccines. Many have expressed worry regarding the possibility of reduced efficacy of the currently available coronavirus vaccines, which were developed to combat the “wild type” virus that became pandemic one year ago. With numerous variants emerging since, scientists have begun to assess whether the game-changing vaccines being rolled out globally will still work against them.

In a randomized trial published in the New England Journal of Medicine today, researchers tested the Oxford/AstraZeneca viral vector vaccine in participants ages 18-65 years old in South Africa. Participants either received two “standard dose” vaccines or saline injections as placebo 28 days apart.

Among those that received the vaccine, 2.5 percent were diagnosed with mild-to-moderate covid-19 compared with 3.2 percent among those who received the placebo. Nearly all (93 percent) of those diagnosed with covid-19 were infected with the B.1.351 SARS-CoV-2 variant. Overall vaccine efficacy was quite low (at 22 percent) and even lower amongst those with confirmed cases of the B.1.351 variant (at 10.4 percent).

Yes, the results of this trial are disappointing. We would like to see good efficacy of the vaccine in protecting people from any degree of covid-19, asymptomatic or otherwise. However, we suspect that some headlines reporting this study to the mainstream media will present the findings as more doomsday than is owed. The results from this trial do not necessarily imply the Oxford/AstraZeneca vaccine is “useless” against this variant. While it is possible that this vaccine has reduced efficacy against more serious or critical covid-19, we simply do not know that from these data; there were no cases of severe covid-19 in either the placebo or vaccine group in the present trial. In fact, as the recent larger Johnson & Johnson trial in South Africa showed (which included many patients infected with the B.1.351 variant), at least one adenovirus vector vaccine constructed similarly to the Oxford/AstraZeneca vaccine has been shown to have good efficacy against the B.1.351 variant in achieving the overarching goal of reducing the number of people who get severely or critically with covid-19.

In sum, we now have data to suggest that adenovirus vaccines may not protect against mild and moderate covid-19 (Oxford/AstraZeneca) and data to suggest that this type of vaccine may yet still protect against serious and critical illness (Johnson and Johnson). If these data were to hold up, the pandemic would indeed eventually end even in places that only have access to these adenovirus options. We need to remember that the short-term goal of getting out of this pandemic is not eliminating mild and moderate disease; those cases we can live with. The way out of the pandemic is by eliminating the high number of hospitalizations and deaths; the high prevalence of such widespread and severe disease we can’t continue to abide.