July 2021
Dr Marieke Brauer – Clinical Virologist
Ampath | ampath.co.za
Background
- The Delta SARS-CoV-2 variant was first detected in India in October 2020.
- It has since spread to 85 countries worldwide.
- Due to increased transmissibility, Delta rapidly became the dominant strain in many regions.
- On 26 June 2021, it was announced that Delta is increasingly prevalent in South Africa, surpassing other variants in most provinces.
Key Characteristics and Implications of the Delta Variant
✅ Transmissibility
- Delta is 30% to 60% more transmissible than previous variants.
✅ Severity of Illness
- Preliminary reports suggest a potential increase in hospitalisation risk, although this has not been definitively confirmed.
✅ Clinical Presentation
- Early symptoms may differ from previous variants:
- Headache
- Sore throat
- Runny nose
- Fever
- Cough and loss of smell appear to be less common than in earlier variants.
✅ Susceptibility
- Preliminary data suggests that children and young adults may be infected more frequently with Delta than with earlier variants.
✅ Risk of Reinfection
- Reduced neutralisation by antibodies has been observed in people previously infected, including those who recovered from the Beta variant.
- This suggests a possible increased risk of reinfection.
✅ Impact on Diagnostic Testing
- No impact on the performance of current SARS-CoV-2 RT-PCR tests has been reported.
- However, routine RT-PCR assays cannot distinguish between variants.
✅ Impact on Vaccine Efficacy and Effectiveness
Pfizer-BioNTech
- Effectiveness against symptomatic disease:
- One dose: 33% (vs. 49% against Alpha)
- Two doses: 88% (vs. 93% against Alpha)
- Protection against hospitalisation:
- One dose: 71% (vs. 76% against Alpha)
- Two doses: 92% (vs. 86% against Alpha)
AstraZeneca
- Effectiveness against symptomatic disease:
- One dose: 33% (vs. 51% against Alpha)
- Two doses: 60% (vs. 66% against Alpha)
- Protection against hospitalisation:
- One dose: 94% (vs. 83% against Alpha)
- Two doses: 96% (vs. 94% against Alpha)
Johnson & Johnson
- J&J announced that their vaccine shows strong and sustained activity against Delta.
- Peer-reviewed data is pending.
Final Notes
- Current SARS-CoV-2 RT-PCR platforms used by Ampath can detect the Delta variant.
- However, they cannot differentiate between variants.
📌 For additional information, please contact your local Ampath pathologist.
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