Credit ACIP/CDC
#16,417
Last summer, in UK SAGE: Can We Predict the Limits of SARS-CoV-2 Variants and their Phenotypic Consequences?, we looked at a number of plausible scenarios for the future course of the COVID pandemic, including the emergence of a more severe variant, and the (more likely) emergence of a vaccine resistant variant.
While Omicron appears to be no more severe than Delta - and perhaps even less so - we do seem to be facing a more resistant virus, against both infection and vaccine induced immunity.
We've a new study from the University of Hong Kong that finds that two doses of the Pfizer, and China's Sinovac vaccine, appear to be no match for Omicron. But first, a quick look at the scenario presented by SAGE last summer.
3. Antigenic ‘shift’: Natural recombination events that insert a different spike gene sequence (or partial sequence) from human CoVs MERS-CoV (highly unlikely due to the low frequency of MERS-CoV infections), or from currently circulating endemic human CoVs (more likely due to the prevalence of these viruses). This would recombine into the ‘body’ of SARS-CoV-2 that is capable of high replication in human cells. The consequence could be a virus that causes disease at a level similar to COVID-19 when it first emerged but against which our current battery of spike glycoprotein-based vaccines would not work.Likelihood: Realistic possibility.Impact: High for a completely new spike, medium/low if a spike from a seasonal CoV is introduced since we expect a proportion of the population to have antibodies to these endemic viruses.What could we do?
In the case of introduction of a completely different spike glycoprotein, a similar vaccine platform could be rapidly employed as has been used successfully on the original Wuhan SARS-CoV-2 and subsequent variants. However, there would be a time lag for roll out whilst these vaccines were generated in sufficient quantities to control and mitigate the effects of infection.
While this scenario appears eerily spot on, it was just one of several presented. The full report is very much worth reading, since the other scenarios remain on the table.
Moving on, yesterday Hong Kong researchers released a preprint that shows 2 doses of the Pfizer vaccine aren't enough to defeat omicron, but a booster appears to increase protection significantly.
For China's ubiquitous Coronavac - the most delivered vaccine in the world - the news appears worse, as it isn't clear whether a 3rd dose is enough to improve performance.
The press release from HKU, and a link to the preprint, follow. I'll have a brief postscript after the break.
HKU microbiologists find that two doses of BNT162b2 (BioNTech ) or Coronavac (Sinovac) vaccines are inadequate against Omicron virus variants
14 Dec 2021
Researchers at the Department of Microbiology of the University of Hong Kong (HKU) have found that most individuals after given two doses of the vaccine (either BioNtech or Coronavac) do not produce sufficient levels of serum antibodies against the new Omicron virus variant. The public is advised to get a third dose of the vaccine as soon as possible while awaiting for the next generation of more matched vaccine. The results of the study have been accepted for publication in the medical journal Clinical Infectious Diseases. It is available online as a preprint.
Background
The SARS-CoV-2 Omicron variant, first identified in November 2021, is spreading worldwide. This variant is particularly worrisome due to the large number of mutations in the virus that could affect infectivity or vaccine efficacy. To assess the effectiveness of existing COVID-19 vaccines in Hong Kong against this novel variant, researchers at the Department of Microbiology tested the ability of serum samples from fully vaccinated recipients to neutralize this variant. Serum neutralizing antibody titers are currently the only easily reproducible surrogate marker of protection against COVID-19.
Research findings
To test the ability of vaccine recipients' serum antibodies to neutralize the Omicron variant, the team used sera from two groups of vaccine recipients who have received two doses of BNT162b2 (BioNtech) or Coronavac. Each group consists of 25 people.
The study aims to more fully evaluate the health risk of the Omicron variant to the Hong Kong population and the need for a universal third dose.
Two Omicron variants present in Hong Kong were tested, one from South Africa and the other from Nigeria (with the additional R346K mutation). The ability of serum antibodies to neutralize the Alpha, Beta, and Delta strains was also tested as a control.
Only five out of 25 Biontech vaccine recipients had neutralizing ability against the Omicron variant virus, and the vaccine efficiency was significantly reduced to 20 - 24%. Compared to the original SARS-CoV-2 strain, the titer of neutralizing antibodies against the Omicron variant has decreased by 36 - 40 fold.
None of the serum of the 25 Coronavac vaccine recipients contain sufficient antibody to neutralize the Omicron variant at the limit of 1 in 10 dilution.
Implications of the study
1. The Omicron variant virus was able to reduce the effectiveness of two doses of COVID-19 vaccine, particularly against Coronavac. Therefore, COVID-19 vaccine recipients or even those recovered COVID-19 patients may be at a higher risk of breakthrough or reinfection. Our findings suggest that the design of the next generation of COVID-19 vaccine should consider sufficient coverage against this novel viral variant.
2. A third dose of COVID-19 vaccine is needed to enhance the antibody response against the Omicron variant.
3. Whether a third dose of the present Coronavac vaccine will enhance the neutralizing antibody response against the Omicron variant remains to be determined.
About the Research Team
Kwok-Yung Yuen, Henry Fok Professor of Infectious Diseases, Chair Professor of Microbiology, Li Ka Shing Faculty of Medicine, and Member of the Chinese Academy of Engineering and Director of the State Key Laboratory of Emerging Infectious Diseases, The University of Hong Kong
Kelvin To, Clinical Associate Professor, Department of Microbiology
Honglin Chen, Professor, Department of Microbiology
This research is funded by the Health and Medical Research Fund, the Food and Health Bureau, The Government of the Hong Kong Special Administrative Region.
The preprint of the study "Neutralization of SARS-CoV-2 Omicron variant by sera from BNT162b2 or Coronavac vaccine recipients" is posted at:
For those who already have two doses under their belt, the message is simple; get the booster. Some countries are lowering the waiting time to get a booster (see Denmark Reduces Time Between 2nd COVID Shot And Booster), and based on what we are seeing, I suspect more will follow.
But for those who haven't yet started (or completed) their initial course of the vaccine, the challenges from Omicron are greater.
You still have to space out the vaccines in order to get the proper response. And that means that starting from scratch, if they get their first shot today, they are still at least 4 or 5 months away from getting a booster.
It is still worth doing, since we don't know what may come after Omicron, and the first two doses may still reduce the severity of infection. But the full benefits won't come for several months.
While roughly 42% of the world's population are considered `fully vaccinated', less than 5% have had a booster shot. Which means - `milder' or not - Omicron has the distinct advantage of entering a target-rich environment in 2022.
