AstraZeneca’s vaccine does not protect against the South African variant of SARS-CoV-2

by Sam Sun

Will other vaccines provide long-term protection against this variant?

The AstraZeneca vaccine offers essentially zero protection against the South African variant of SARS-CoV-2, dubbed B.1.351. In contrast, the JNJ vaccine and Novavax vaccine offer some protection against B.1.351.

  • AstraZeneca vaccine
    • 10.6% efficacy against mild-to-moderate COVID-19 in HIV-negative participants 
    • 93% of COVID-19 due to the B.1.351 variant
  • JNJ vaccine
    • 57% efficacy against moderate-to-severe COVID-19 in HIV-negative or HIV-positive participants 
    • 95% of COVID-19 due to the B.1.351 variant
  • Novavax vaccine
    • 60% efficacy against COVID-19 in HIV-negative participants 
    • 93% of COVID-19 due to the B.1.351 variant

South Africa initially granted emergency use authorization to AstraZeneca’s vaccine for COVID-19, based on worldwide clinical trials. However, with this preprint publication, South Africa halted its rollout of AstraZeneca’s vaccine. South Africa plans to rollout JNJ and Pfizer’s vaccines in the next few weeks. 

The WHO’s Strategic Advisory Group of Experts on Immunisation still recommends rollout of AstraZeneca’s vaccine, even in countries like South Africa with the B.1.351 variant of SARS-CoV-2. Because the JNJ and AstraZeneca vaccines are both based on adenovirus vectors, and may elicit similar T-cell responses, it’s possible (but speculatory) that AstraZeneca’s vaccine also protects against severe COVID-19 disease from the B.1.351 variant.

Finally, we speculate that all first-generation COVID-19 vaccines are ineffective against the B.1.351 variant of SARS-CoV-2, with vaccine efficacy under 50%, if 6 months or more have elapsed since vaccination. Of note, AstraZeneca’s vaccine trial has collected more long term clinical data in South Africa than any other vaccine trial:

AstraZeneca’s vaccine trial in South Africa identified cases of COVID-19 for 180 days. Although Moderna, Pfizer, and the Gamaleya Institute did not conduct their vaccine trials against the B.1.351 variant of SARS-CoV-2, their published studies identified cases of COVID-19 for 110 days120 days, and 80 days, respectively. At 120 days, AstraZeneca’s vaccine also seems to confer partial protection against the B.1.351 variant, with 50-60% vaccine efficacy (see below, or see attachment). Post-vaccination, neutralizing antibody titers decline over time, and long term protection against COVID-19 is currently unknown for any vaccine. In fact, Moderna’s CEO stated that long term immunity may wane, in the context of protection against the B.1.351 variant. 

The WHO is optimistic in its speculation: 

  • Perhaps, AstraZeneca is as effective as JNJ and Novavax’s vaccines, with partial protection (~50%) against severe COVID-19 disease 

However, we offer the pessimistic speculation: 

  • Perhaps, JNJ and Novavax are as ineffective as AstraZeneca’s vaccine, with little to no protection (~10-20%) against mild-to-moderate COVID-19 disease starting 6 months after vaccination

Of course, we await peer-reviewed publication of JNJ and Novavax phase 3 clinical trial data for their vaccines.

In light of the possibility that first-generation vaccines are ineffective against the B.1.351 variant, we offer these suggestions:

  • Prioritization of the development of COVID-19 vaccine boosters against novel variants of SARS-CoV-2, with an expedited regulatory pathway
  • Vigilance with SARS-CoV-2 testing, with ongoing assessments of long term vaccine efficacy (>6 months) against B.1.351 and other novel variants of SARS-CoV-2


Medrxiv paperReuters 1/27/2021Reuters 2/8/2021Reuters 2/10/2021

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