Coronavirus Research Tracking - 10 December - Omicron edition
Coronavirus Research Tracking - 10 December - Omicron edition
This explainer is more than 90 days old. Some of the information might be out of date or no longer relevant. Browse our homepage for up to date content or request information about a specific topic from our team of scientists.
This article has been translated from its original language. Please reach out if you have any feedback on the translation.
Early data on reduced neutralisation of Omicron after prior infections or vaccinations.
Early data on reduced neutralisation of Omicron after prior infections or vaccinations.
Publication
What our experts say
Context and background
Resources
The Research Tracker is prepared by Dr Robert Hickson for the NZ Science Media Centre.
Omicron-related papers
The UK Health Security Agency produced an updated risk assessment of the Omicron variant on 8 December, prior to the release of some of the studies summarised below.
The European Centre for Disease Prevention and Control has confirmed 337 Omicron variant cases in the EU as of 8 December. For cases where there is information on severity, all were either asymptomatic or mild. The Centre cautions that this number of cases is too low to reliably compare outcomes with other variants.
Neutralisation of Omicron
Several papers or provisional data have appeared in the last few days investigating how well the Omicron variant is neutralised by vaccine or earlier infection-generated antibodies. These are all lab-based studies, involving small numbers of subjects. (See also the 6 October Tracker for an earlier report).
The methods also differ between each study, so there is still uncertainty about the real-world impacts of the Omicron variant. However, all the studies indicate that neutralisation ability against Omicron is often reduced after two vaccine doses.
Neutralisation activity affects how well an infection is controlled. What hasn’t yet been studied is whether cellular immunity (mediated by T cells) is reduced against Omicron. Early analyses indicate that the mutations seen in Omicron are less likely to affect T cell recognition, so protection against serious disease may be maintained from earlier infections or vaccinations.
Plasma from previously vaccinated people (Pfizer/BioNTech) showed a reduced ability to neutralise the Omicron variant, compared with an early pandemic strain, particularly if they had no prior SARS-CoV-2 infection. The reduction in neutralisation was on average 40-fold lower, although neutralisation ability was less impacted in those with a prior infection.
The study is based on a small number of people (sera from six who had a prior infection and vaccination, and six who were vaccinated but had not been infected). Samples were taken from people who had been vaccinated within the last month, while infections had occurred over a year previously. The paper has not yet been peer reviewed.
Another study found the reduction in neutralisation of the Omicron variant is very variable between individuals. Compared to an early pandemic strain, reduction was between one and 23-fold. Similar neutralisation variability was seen for the Delta variant. The study involved serum samples from 34 people with previous infections. The findings are provisional. The paper has not yet been peer reviewed.
Pfizer and BioNTech released data in a press release that indicated a 25-fold, or more, reduction in neutralising activity against Omicron after two vaccine doses, compared with an early viral strain.
A third dose of the vaccine boosted neutralising antibody levels about 25-fold higher than two doses, potentially restoring the effectiveness of the vaccine. The press release notes that CD8+ T cells are also boosted after a third dose, which could maintain protection against severe Covid-19.
Many details of the study are not included in the press release. The Pfizer results are, though, prompting some scientists and health agencies to encourage third vaccine doses sooner rather than waiting for a six month interval.
The NZ Science Media Centre produced an expert reaction to the Pfizer data.
The fourth short study included sera from people vaccinated with the Pfizer (after 2 or 3 doses), Moderna + Pfizer, & AstraZeneca/Oxford + Pfizer vaccines. Reductions in neutralisation activity ranged from 11 to 37-fold against Omicron, compared with the Delta variant. Sera from those who received the AstraZeneca + Pfizer vaccine combination did not neutralise Omicron.
Sera from only one or two people with each vaccine combination were involved, so further research is needed. The paper has not yet been peer reviewed.
The Research Tracker is prepared by Dr Robert Hickson for the NZ Science Media Centre.
Omicron-related papers
The UK Health Security Agency produced an updated risk assessment of the Omicron variant on 8 December, prior to the release of some of the studies summarised below.
The European Centre for Disease Prevention and Control has confirmed 337 Omicron variant cases in the EU as of 8 December. For cases where there is information on severity, all were either asymptomatic or mild. The Centre cautions that this number of cases is too low to reliably compare outcomes with other variants.
Neutralisation of Omicron
Several papers or provisional data have appeared in the last few days investigating how well the Omicron variant is neutralised by vaccine or earlier infection-generated antibodies. These are all lab-based studies, involving small numbers of subjects. (See also the 6 October Tracker for an earlier report).
The methods also differ between each study, so there is still uncertainty about the real-world impacts of the Omicron variant. However, all the studies indicate that neutralisation ability against Omicron is often reduced after two vaccine doses.
Neutralisation activity affects how well an infection is controlled. What hasn’t yet been studied is whether cellular immunity (mediated by T cells) is reduced against Omicron. Early analyses indicate that the mutations seen in Omicron are less likely to affect T cell recognition, so protection against serious disease may be maintained from earlier infections or vaccinations.
Plasma from previously vaccinated people (Pfizer/BioNTech) showed a reduced ability to neutralise the Omicron variant, compared with an early pandemic strain, particularly if they had no prior SARS-CoV-2 infection. The reduction in neutralisation was on average 40-fold lower, although neutralisation ability was less impacted in those with a prior infection.
The study is based on a small number of people (sera from six who had a prior infection and vaccination, and six who were vaccinated but had not been infected). Samples were taken from people who had been vaccinated within the last month, while infections had occurred over a year previously. The paper has not yet been peer reviewed.
Another study found the reduction in neutralisation of the Omicron variant is very variable between individuals. Compared to an early pandemic strain, reduction was between one and 23-fold. Similar neutralisation variability was seen for the Delta variant. The study involved serum samples from 34 people with previous infections. The findings are provisional. The paper has not yet been peer reviewed.
Pfizer and BioNTech released data in a press release that indicated a 25-fold, or more, reduction in neutralising activity against Omicron after two vaccine doses, compared with an early viral strain.
A third dose of the vaccine boosted neutralising antibody levels about 25-fold higher than two doses, potentially restoring the effectiveness of the vaccine. The press release notes that CD8+ T cells are also boosted after a third dose, which could maintain protection against severe Covid-19.
Many details of the study are not included in the press release. The Pfizer results are, though, prompting some scientists and health agencies to encourage third vaccine doses sooner rather than waiting for a six month interval.
The NZ Science Media Centre produced an expert reaction to the Pfizer data.
The fourth short study included sera from people vaccinated with the Pfizer (after 2 or 3 doses), Moderna + Pfizer, & AstraZeneca/Oxford + Pfizer vaccines. Reductions in neutralisation activity ranged from 11 to 37-fold against Omicron, compared with the Delta variant. Sera from those who received the AstraZeneca + Pfizer vaccine combination did not neutralise Omicron.
Sera from only one or two people with each vaccine combination were involved, so further research is needed. The paper has not yet been peer reviewed.
