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expert reaction to press release from Discovery Health giving real-world information on their Omicron outbreak based on 211000 COVID-19 positive test results in South Africa

A press release from Discovery Health, a private health insurance administrator from South Africa, provides real-world data on the Omicron outbreak in South Africa, and includes collaboration with the South African Medical Research Council (SAMRC) on vaccine effectiveness.


Prof Paul Hunter, Professor in Medicine, UEA, said:

“Without seeing a preprint or the report on which this press release is based it is difficult to get a clear understanding of the validity of these conclusions.  If these are valid conclusions then there are both reassuring and worrying findings.  The report that reinfections are more common with omicron has already been published and the evidence is strong that omicron can increase the risk of infection in people who have already had a covid infection  Whilst this study did not include data on infection following vaccine it would be a safe bet that breakthrough infections would also be more common with omicron.

“That 2 doses of Pfizer vaccine provides 70% protection against severe disease requiring hospitalisation is good news and would place the risk around the low escape scenario in the London School of Hygiene and Tropical Medicine model  But South Africa has rolled out their vaccination programme more recently than the UK so we have likely seen more waning in protection.  Even so after adjusting for vaccination risk of hospitalisation is about 29% lower than in original covid variant, though I suspect this difference is due to cross immunity from a high proportion of the South African population having already had covid.

“Although the data are preliminary and based on relatively small numbers there does appear to be a 20% increase in the risk of children being admitted to hospital with covid.  We should not draw definitive conclusions about the risk to children yet, but we need to monitor this closely to see whether there is a corresponding increase in the UK.

“Overall this data if supported by more detailed analyses provides optimism that though immunity to infection by omicron is less, immunity to severe disease, though diminished, may hold up better.”


Dr Peter English, Retired Consultant in Communicable Disease Control, Former Editor of Vaccines in Practice, past Chair of the BMA Public Health Medicine Committee, said:

“These are early data – we shouldn’t expect them to be the last word; but they are early indicators of the sort of answers we are likely to expect as we get more data, and as we get data from other countries (like, for example, the data from Denmark, which I haven’t yet managed to digest: ) we will firm up the figures and get a better idea of how they can be generalised to a UK population with a higher vaccination rate and more older people.

“Two things leap out from this press release.

“Two doses of vaccine are 70% effective at preventing hospitalisation.  They are not ineffective; but they are much less effective than the 90-95% protection that two doses provided against hospitalisation (at least for the first 6 months or so).  With a highly infectious variant (and omicron is highly infectious) this still risks a catastrophic number of hospitalisations affecting an already depleted NHS.

“The other highly alarming point is that the omicron variant appears to be more likely to hospitalise children.  We don’t know yet (for obvious reasons) what effect the variant will have on Long Covid in children; but if more are hospitalised, we can expect more Long Covid, too, so it’s not just the very short term consequences (pressure on paediatric beds) that we need to worry about, but the longer-term consequences, too.

“This seems to me like a good reason to move immediately to distance learning for nearly all children.  (I have discussed this in detail wrt previous variants.)  It is hard to understand why, when you could look up the number of HEPA filter units in every classroom in New York State before the 2021 summer holidays; and when we have known for over a year how to control spread in schools, hardly any of the mitigations we should have put in place before schools returned after the summer break are widely in use; and while other countries have been vaccinating 5-11 years for well over a month, UK regulators are still claiming there isn’t enough data to recommend doing that here.

“The report also emphasises that the symptoms in children are NOT the three symptoms listed on the NHS web site – these have been out of date since Delta became prevalent.

“One thing I can’t find in this report is clear information about infection and transmission.  The report refers to “reinfection”, but I suspect it means symptomatic infection – unless they are doing surveys of random samples people with or without symptoms, how would they know?  They may be doing this; but I can’t see information about that in the press release.

“They do tell us that reinfection with omicron variant seems to be more likely if people were infected previously in the earlier, alpha wave of infection than if they were infected in the later, delta wave.  It’s not clear if this is due to the time difference – people infected longer ago may have lower antibody levels and waning immunity; or whether the delta variant is closer, immunologically, to omicron.  A combination of both might apply.

“The reason I’m raising this is because many people who have been vaccinated or previously infected have asymptomatic infection, but may, nevertheless, be infectious.  One of the potential benefits of vaccination is the reduction of transmission, if vaccination significantly reduces the proportion of people who can become infected, and then infect others.  Evidence had started to accumulate that a third vaccine dose has a very significant effect in reducing all infections – not just symptomatic disease – with the delta variant.  Understanding how effective two or three doses of original vaccines will be against the omicron variant will be crucial in managing the evolving pandemic.

“It is difficult to get good data on all (not just asymptomatic) infection, so I have no criticism of the excellent work done by South African colleagues, other than that I’d have liked the press release to be clearer about what they are referring to.

“(I prefer to refer to “third dose” than “booster” because it has become clear that, at least with current vaccines, the primary course must comprise at least three doses.  I would apply the term “booster” to doses given at least 12 months after the previous dose.)

“Note that this press release is extremely cautious about the possibility that omicron might be less virulent.  It says: “Epidemiological tracking shows a steep trajectory of new infections, indicating Omicron’s rapid spread, but so far with a flatter trajectory of hospital admissions, possibly indicating lower severity,” explains Dr 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 following an extensive Delta wave of infections”.”

“We also need to be aware that the age structure of the South African population may be quite different from that of the UK.  You would expect to see fewer severe cases in a population with a smaller proportion of older people.”


Dr Simon Clarke, Associate Professor in Cellular Microbiology, University of Reading, said:

“This press release outlines preliminary observations of Covid-19 in South Africa during the first three weeks of the wave of infections caused by the Omicron.  It shouldn’t be forgotten that in the UK, during the initial epidemic there was a 5 week gap between the first diagnosis and the first death.  A situation report taken in those first few weeks would not have given us an accurate picture of what was about to happen, so we shouldn’t expect these preliminary indications to be a portent of how the Omicron epidemic will play out  here.  We know that infection fatality rates can differ widely amongst countries1 for a mixture of known and unknown reasons and policy makers will rightly bear that in mind.  The impact of booster doses is not taken into account with any of these initial observations, because the South Africans haven’t had a booster program.

“The increased transmissibility of Omicron could easily outweigh any drop in the variant’s ability to cause disease, meaning that it could deliver a much more significant impact to society and the NHS than previous waves of disease.  Similarly, a mass sickness of people who are not ill enough to end up in hospital, but who need to convalesce at home, could deliver a substantial shutdown of public services and slowing of economic activity.”



Prof Russell Viner, Professor of Child and Adolescent Health, UCL, said:

“The most striking feature of covid-19 across all previous variants has been the extreme age effects seen, with the elderly most affected.  These South African data on Omicron in fact also show this – showing very low absolute incidence in children.

“Regarding the suggestion of higher hospitalisation rates in children for Omicron, it is essential to recognise that these are incomplete and partial data.  For each previous variant we saw early claims that children were more affected which turned out later not to be true.  In November 2020 we saw claims that the alpha variant affected children more, and in May-June 2021 we saw similar claims about delta.  Each of these were the result of early partial data and neither turned out to be correct.  This emphasises the importance of being careful about extrapolation from very limited data.

“We cannot of course be complacent and we must carefully watch evolving data on Omicron from South Africa and elsewhere as they emerge.”


Dr Michael Head, Senior Research Fellow in Global Health, University of Southampton, said:

“The real-time data relating to Omicron is (alas) coming thick and fast, so today’s information can easily be superseded by new evidence this time tomorrow.  We also can see from the Discovery Health release that their analyses covers just 3 weeks of data.  Thus, it is important to avoid inferring too much right now from any national scenario.

“For example, the narrative around South Africa is that Omicron may be much milder, whereas reports out of Denmark1 broadly suggests the opposite.  This reflects the uncertainty of new data.  Within that, factors includes the different levels of exposure to COVID-19 and previous infection, levels of vaccination and potential waning of immunity, and also age ranges infected thus far.  We know that COVID-19 is very adept at moving from younger to older populations within a few weeks.

“Is Omicron milder, or more severe than Delta?  Time will tell.  The world’s finest scientists, including many in the global south such as in South Africa, will find out.  For now, national-level decision-makers have to consider that discretion is the better part of valour.”




All our previous output on this subject can be seen at this weblink:



Declared interests

Dr Peter English: “Dr English is on the editorial board of Vaccines Today: an unpaid, voluntary, position.  While he is also a member of the BMA’s Public Health Medicine Committee (and its chair until Oct 2020), this comment is made in a personal capacity.  Dr English sometimes receives honoraria for acting as a consultant to various vaccine manufacturers, most recently to Seqirus.”

None others received.

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