covid: omicron has 1/2 the hospitalization rate vs delta; futility of lockdowns

 A new Technical Briefing was released from the UK on vaccine effectiveness for omicron, finding that omicron had about ½ the rate of severe covid vs delta (see https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1044481/Technical-Briefing-31-Dec-2021-Omicron_severity_update.pdf )

 

Details:

-- this report covered omicron cases, hospitalizations, and deaths until 29 December 2021

-- 198,348 confirmed omicron cases in the UK, identified through sequencing or genotyping in England; and 451,194 probable cases, identified through S-gene target failure (SGTF) [for more info on SGTF, see http://gmodestmedblogs.blogspot.com/2021/04/covid-uk-variant-likely-responds-to.html ]

-- two studies were reported, as noted below

 

Results:

    -- Study 1: approximately half a million omicron cases (including all cases diagnosed in the community and in the first day of hospital admission, and for all age groups), results stratified by age, sex, ethnicity, local area deprivation index, international travel, vaccination status, whether the current infection is a known reinfection or not (though re-infection is substantially under-ascertained):

    -- risk of emergency care visit or hospitalization with omicron: 47% less than Delta, HR 0.53 (0.50-0.57)

    -- risk of hospitalization with omicron: 67% less than Delta, HR 0.33 (0.30-0.37)

    -- vaccine effectiveness: risk of hospitalization for omicron was lower after two and three doses of vaccine

        -- after three doses of vaccine, 81% (77-85%) reduction in the risk of hospitalization versus unvaccinated omicron cases

 

-- Study 2: restricted the analysis to symptomatic cases diagnosed in the community, followed then by a hospital admission (in an attempt to decrease incidental cases of Covid being reported as causing that hospital admission, ie patients being admitted with positive covid test instead of because of it):

    -- risk of hospitalization for symptomatic omicron case through community testing was reduced by 68% (42-82%) versus unvaccinated, adjusting for age, gender, previous positive test, region, ethnicity, clinically extremely vulnerable status, risk group status and study period

    -- vaccine effectiveness against hospitalization: 88% (78-93%) after three doses of vaccine

        -- there was some waning effectiveness against symptomatic cases, but insufficient data to assess the duration of protection against hospitalization (which is expected to last longer). see more data below

 

-- Until December 29, there was a total of 815 individuals with laboratory-confirmed omicron who were admitted from the emergency departments to the hospital

    -- age range was 0-100, median 45.5 years; 61% were at least 40 years old, 31% at least 70

-- 57 people had died within 28 days of omicron diagnosis; the mean time from omicron’s detection day to death was five days; the age of those dying range from 41-99 years

    -- of these hospitalizations, 25% were people who were not vaccinated, 6% received one dose of vaccine more than 21 days before omicron detection day, 43% received a second dose of vaccine more than 14 days before omicron detection day, and 23% had received a third dose or booster more than 14 days before omicron detection day (though it appears that only 25% were unvaccinated, it should be emphasized that in a society with high vaccination coverage, this group is significantly over-represented in hospitalizations)

-- by preliminary analysis, there was also half the risk of hospitalization in children 5-17yo from the omicron versus Delta variants: HR 0.42 (0.28-0.63)

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Here is their graph of admitted cases over time:

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--overall vaccine effectiveness:

    -- comparing vaccine effectiveness for hospital admission within 14 days of a positive test for the omicron versus delta variants:

-- This table shows similar vaccine effectiveness against hospital admission (about an 85% decrease for both variants, with no statistically significant difference after the third dose of vaccine between the omicron and delta variant. Of note, however, the omicron variant did require the booster vaccine to achieve this level of parity

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Vaccine effectiveness against symptomatic diseases after dose 1 and dose 2 for Delta (black squares) and Omicron (grey circles) for recipients of 2 doses of Pfizer vaccine as the primary course and Pfizer or Moderna as a booster:

-- The study did find waning effectiveness of boosters for symptomatic covid cases, where two doses of the mRNA vaccines had vaccine effectiveness drop from 65 to 70% down to around 10% by 20 weeks after the second dose; 2 to 4 weeks after the booster dose, vaccine effectiveness ranged from around 65 to 75% dropping to 55 to 70% at weeks 5 to 9 and 40 to 50% after 10 weeks post booster

Commentary:

--as found in South Africa:

    -- the omicron variant was less severe overall than the prior delta one

    -- it was impressive that the large number of cases admitted or transferred to the hospital went through a large peak but then a large falloff over a 1 to 2 week (a big burst, then combo of vaccines and lots of new cases leading to some herd immunity and a dramatic falloff in cases??)

-- The booster shot was clearly very important for decreasing hospital admission for the omicron variant, bringing the vaccine effectiveness to the same level as for the delta variant

   -- though there was somewhat less protection against all symptomatic cases, with evident waning immunity within a few months

-- these data suggest significant vaccine protection against hospitalizable omicron infections. However, it is important to understand this in perspective: the huge transmissibility and peaks of omicron infections will still translate to very large numbers of people needing hospitalizations

 

Limitations:

-- not enough granular data on subgroup analysis of vaccine effectiveness with omicron, stratified by risk factors

    -- despite the very large databases in this study, there were relatively few hospital admissions (815 admissions and 57 deaths), so some subgroup analyses may not have been statistically valid...  (would still have been useful to see the numbers)

-- no information about outcomes from hospitalization, % in ICU and for how long, % on ventilators, length of stay in those hospitalized, likely longer-term sequelae (renal failure, stroke, MI, chronic lung disease....), though it does seem that lung tissue is less targeted by omicron

-- there are concerns about extrapolating data from other countries, given differences in many potential important factors: presence of other viruses in that community, including the 4 common annual coronaviruses, which potentially could affect omicron virulence; other local epidemiologic factors that might affect viral transmission (e.g. use of mitigation strategies); other sociodemographic differences that might affect disease acquisition and outcomes

-- the numbers of people with Covid infections is likely increasingly underestimated: there is the large number of asymptomatic cases (and perhaps the % asymptomatic varies by the variant); more people are wanting to be tested but access to public testing in the US is getting more difficult; and more people are doing home-based tests and these results never make it to the databases (in the latter case, we will see a better reliability of data for the sicker patients in the hospital, since these will generally make it into databases, and the increased representation of severe cases in the databases may make it seem that a higher % are hospitalized than before)

so, a few hopeful points amid the sea of gloom:

-- though the hospitals are being inundated with covid cases, it seems that the omicron variant has a lower percentage of those with severe disease (though there still are the lurking delta cases)

-- and, given the transmissibility of omicron, and the huge numbers of people who get infected (with a skew to being less sick), we are (hopefully) going to follow the curves of UK and South Africa, with a remarkably rapid increase in cases (as we are seeing now), then followed by a downward slope about as steep in the opposite direction....

-- also, with the anticipated dread of omicron, many people have been getting boosters: a component of helping decrease the reservoir of SARS-CoV-2 that can mutate into potentially worse variants in the future [though Israel is now authorizing a second booster, shot #4, for older folks; and many in the US are doing so without authorization]

so here's to starting the new year on a bit of an optimistic note!!!

and, for those of us who are very concerned about the possibility of future lockdowns:  there was an article suggesting that lockdowns are not only remarkably disruptive to our lives but of unclear benefit:  see https://thegrayzone.com/2021/12/03/flattening-curve-global-poor-covid-lockdowns-human-rights-vulnerable/, thanks to Paul Susman for sending this to me). their argument is that studying the various global lockdowns in the past, there is no clear benefit, but there is clear death and economic devastation. the arguments supporting lockdowns relied on very faulty computer modeling, resulted in significant morbidity and mortality (delayed medical visits, screenings, etc), more drug/alcohol use/suicides, severe financial and social consequences,  pretty much all of these disproportionately affected the poor (and leading to many, many more billionaires in several vaccine-manufacturers, online retailers, etc). so, even if things get worse, maybe we can avoid the implementation of lockdowns?????

geoff

 

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