Discovery Health, South Africaʼs largest private health insurance administrator, has released at-scale, real-world analysis of the Omicron outbreak based on 211,000 COVID-19-positive test results in the country.
The findings show that the two-dose Pfizer-BioNTech vaccination provides 70% protection against severe complications of COVID-19 requiring hospitalisation, and 33% protection against COVID-19 infection, during the current Omicron wave.
For those who had previously been infected with COVID-19, the risk of reinfection with Omicron is significantly higher, compared with earlier variants.
However, the risk of hospital admission among adults diagnosed with COVID-19 now is 29% lower for the Omicron variant infection compared with infections from the D614G mutation in South Africaʼs first wave in mid-2020, after adjusting for vaccination status.
As far as children are concerned, despite very low absolute incidence, preliminary data suggest that children have a 20% higher risk of hospital admission in the Omicron-led fourth wave, compared with the first wave.
Discovery said it was important to note that these insights relate to data from the first three weeks of the Omicron-driven wave in South Africa, so should be considered preliminary, as they could change as the wave progresses. The data are also confounded by various factors, including high sero-prevalence of COVID-19 antibodies in the South African population as a whole.
“Superb genetic surveillance by the Network for Genomic Surveillance in South Africa identified that Omicron infection accounts for more than 90% of new infections in South Africa, and has displaced the formerly dominant Delta variant,” said Dr Ryan Noach, CEO of Discovery Health. “The Omicron-driven fourth wave has a significantly steeper trajectory of new infections relative to prior waves. National data show an exponential increase in both new infections and test positivity rates during the first three weeks of this wave, indicating a highly transmissible variant with rapid community spread of infection.”
Real-world data relating to Omicron experience critical to guiding global response
With more than 3,7m clients, Discovery Health has extensive data relating to claims and the utilisation of the private health system.
“Over the past month, our clinical research and actuarial teams have carried out the first at-scale analysis of Omicronʼs real-world impact,” he added, “partnering with world-leading researchers from the South African Medical Research Council (SAMRC) to provide insights into the vaccine effectiveness of the Pfizer-BioNTech vaccine against infections and severe disease linked to Omicron infection.”
Discovery Health further explored various other components of Omicron infection, including the rate of spread, the severity of illness relative to prior waves, clinical manifestations, and the relative reduction of risk conferred by prior proven COVID-19 infection.
The detailed vaccine effectiveness analysis in collaboration with the SAMRC includes more than 211,000 positive COVID-19 test results, 41% from adult members who had received two doses of the Pfizer-BioNTech vaccine.
Approximately 78 000 of these positive COVID-19 test results were attributed to Omicron infections between 15 November 2021 and 7 December 2021.
“Laboratory analysis has provided early insights into potential reduction in the effect of neutralising antibodies against the Omicron variant,” said Noach. “However, there remains urgency around establishing real-world data on Omicron across all areas of impact. Our research is based on a rich and significant sample, and also relates directly to the experience of the first country in the world to face a COVID-19 wave driven by Omicron.”
Two-dose Pfizer-BioNTech vaccination provides significant protection against hospitalisation in people with Omicron infection, the collaboration with leading scientists at the SAMRC had found.
“We used a test-negative design methodology to establish the Pfizer-BioNTech COVID-19 vaccineʼs real-world effectiveness against hospital admission from Omicron,” said Shirley Collie, Chief Health Analytics Actuary at Discovery Health.
“We carried out three carefully constructed sensitivity analyses, with consistent results across each analysis supporting the veracity of our findings. These findings were reviewed by scientists at the SAMRC with whom we have collaborated in multiple areas of our pandemic-related research to date.”
The result shows that vaccinated individuals who received two doses of the Pfizer-BioNTech vaccine had 33% protection against infection, relative to the unvaccinated, in the first weeks of South Africaʼs Omicron-driven fourth wave. This represents a significant drop from the 80% protection against infection afforded during the earlier period, probably on the basis of lower antibody susceptibility, following the extensive spike protein mutations in the Omicron variant.
Encouragingly, though, the result shows that these same vaccinated people who received two doses of the Pfizer-BioNTech vaccine had 70% protection against hospital admission in this same period. While protection against hospital admission was reduced from 93% in the Delta-driven wave, 70% is still regarded as very good protection.
President of the SAMRC Professor Glenda Gray said, “We are extremely encouraged by the results of Discovery Healthʼs analysis. It is important to be able to demonstrate to the public that in a real-world setting – in the presence of a highly transmissible new COVID-19 variant – the Pfizer-BioNTech vaccine provides good protection against severe disease and hospitalisation.”
Furthermore, the analysis demonstrates that protection against hospital admission is maintained across all ages, in people from 18 to 79 years, with slightly lower levels of protection for the elderly (67% in people aged 60 to 69 and 60% for people aged 70 to 79). Protection against admission is also consistent across a range of chronic illnesses, including diabetes, hypertension, hypercholesterolemia and other cardiovascular diseases.
Omicron reinfection risk significantly higher compared to prior variants
“With each successive wave of COVID-19 infection in South Africa, we have investigated the durability of immunity after previous infection with COVID-19 – in other words, the risk of reinfection,” said Collie.
“Overall, the risk (after prior infection) has increased over time, with Omicron resulting in significantly higher rates of reinfection compared with prior variants.”
People who were infected with COVID-19 in South Africaʼs third (Delta) wave face a 40% relative risk of reinfection with Omicron.
People who were infected with COVID-19 in South Africaʼs second (Beta) wave face a 60% relative risk of reinfection with Omicron.
“Those who had a documented infection in South Africaʼs first wave, and therefore were likely to have been infected with the SARS CoV-2 virus carrying the D614G mutation, face a 73% risk of reinfection compared with those without previous documented infection,” added Collie.
The collaborators also investigated Omicronʼs clinical impact relative to other SARS-CoV-2 variants.
“Epidemiological tracking shows a steep trajectory of new infections, indicating its rapid spread, but so far with a flatter trajectory of hospital admissions, possibly indicating lower severity,” said Noach. “This lesser severity could, however, be confounded by the high seroprevalence levels of SARS CoV-2 antibodies in the general South African population, especially after an extensive Delta wave of infections. Adults are experiencing a 29% lower admission risk relative to the first wave of infection, dominated by D614G, in early 2020. Furthermore, hospitalised adults currently have a lower propensity to be admitted to high-care and intensive-care units, compared with prior waves.”
Preliminary observations on Omicron experience in children
“Although children continue to show a very low incidence of severe complications after COVID-19, our data show that children under age 18 have a 20% higher risk of admission for complications of COVID-19 when infected with Omicron,” Collie said.
“These are early data and require careful follow-up. However, this trend aligns with the warning from South Africaʼs National Institute for Communicable Diseases (NICD) in recent days that during our third wave of infection (June to September 2021) they had seen an increase in paediatric admissions and now, in the fourth wave, are seeing a similar increase in admissions for children under five."
Anecdotal reports from hospitals in South Africa show that most COVID-19 diagnoses in children admitted to hospital are co-incidental – many children who are admitted for non-COVID-19-related conditions, and who are not experiencing COVID-19 complications, test positive for COVID-19 on routine screening tests.
It is also important to note that Discovery Healthʼs analysis shows the risk of children testing positive for COVID-19 infections is significantly lower than in adults.
“Children were 51% less likely to test positive for COVID-19 compared with adults in the Omicron period and, overall, the risk of children being admitted to hospital for COVID-19 complications remains low,” said Collie.
Where children require admission for complications of COVID-19, the primary diagnoses are bronchiolitis and pneumonia, often with severe gastrointestinal symptoms and dehydration.
“Most children present with mild disease, with symptoms like a sore throat, nasal congestion, headache and fever that resolves within three days,” Noach said.
“We are encouraged that the Pfizer-BioNTech vaccine continues to offer high levels of protection from severe COVID-19 illness. We hope the current experience of COVID-19 caused by the Omicron variant – mild disease, mainly – will remain unchanged. However, we are concerned that health systems could still come under pressure considering the high rate of spread, and consequent high sudden infection burden.
“The importance of vaccination in the current context is unquestionable, as conclusively demonstrated in the research. At the same time, we urge adherence to the important measures of distancing, avoiding public gatherings, mask wearing and hygiene precautions.”
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