Researchers from the University of Oxford have analysed the impact of the Omicron COVID-19 variant of concern on one of the immune responses generated by vaccination. Using blood samples from individuals who had previously received two doses of the Oxford-AstraZeneca or Pfizer-BioNTech vaccines as part of the Com-COV study, and a live virus isolate, they demonstrate substantial decrease in neutralising titres – a measure of the level of neutralising antibodies generated in responses to vaccination against, or infection from, COVID-19. Here are some answers to frequently asked questions which the team have put together.
What are neutralising antibody titres?
Neutralising antibody titres refer to the level of antibodies, typically in our blood, that can directly kill a specific virus. This level may derive from natural infection, vaccination or a mix of both.
What role do neutralising antibodies play in helping us to fight a COVID-19 infection?
Neutralising antibodies can bind directly to the coronavirus – in most cases to the spike protein – and prevent the virus entering cells. This prevents the virus from making copies of itself, spreading throughout the body and causing disease. The more neutralising antibodies present, the more effectively this can be achieved.
Why do we test for neutralising antibodies?
Neutralising antibodies block the virus from entering our cells and in doing so can stop infections spreading further in our bodies. They are one of the ways in which our immune system can prevent disease.
What further research is needed to fully understand if the vaccines remain effective against the Omicron variant?
The UK Health Security Agency (UKHSA) has published early estimates that of vaccine effectiveness against symptomatic infection find it is significantly lower against Omicron infection compared to Delta infection. Nevertheless, a moderate to high vaccine effectiveness of 70-75% is seen in the early period after a booster dose.
Dr Mary Ramsay, Head of Immunisation at the UKHSA, has said: ‘These early estimates should be treated with caution but they indicate that a few months after the second jab, there is a greater risk of catching the Omicron variant. We expect the vaccines to show higher protection against the serious complications of COVID-19, so if you haven’t had your first two doses, please book an appointment straight away.’
Using only data generated in one type of laboratory experiment, in this case neutralisation assays, can sometimes oversimplify how our bodies fight infection, so we also need real-world data.
We also need to understand the role of other antibodies, and T-cells, which function by different mechanisms and were not measured by these tests.
We may see in time that these other parts of our immune system can make up for the reduction in neutralising antibody, something we have seen with previous variants of COVID-19, where real-world effectiveness data has shown that vaccines continue to prevent severe illness, and hospitalisation.
The role of T-cells, which research shows may play an important role in cross protection against different coronaviruses, as well as variants of the virus causing COVID-19, is something that also needs more research.
We are also looking into the effects of booster vaccination on these neutralising antibodies using blood samples from our COV-Boost study and will publish our findings in due course.
Will you be updating your vaccine?
As with any new variant, we will carefully evaluate the implications of the emergence of Omicron for vaccine immunity. Despite the appearance of new variants over the past year, existing vaccines have continued to provide very high levels of protection against severe disease and hospitalisation. However, we have the necessary tools and processes in place for rapid development of an updated Omicron specific COVID-19 vaccine if it should be necessary.
Why were you able to use blood samples from the COM-COV study to study new variants?
It was one of our exploratory goals in the original study design to be able to study blood samples against variants. Participants gave consent for us to keep their samples for this purpose.
The COM-COV2 study looked at other dosing schedules, (link to info on study), will you be testing these against the Omicron variant?
It is our intent to test samples from the COM-COV2 study, and we will publish our findings in due course.
The COV-Boost study looks at booster shots – are you testing blood from this study against Omicron?
It is our intent to test samples from the COV-Boost study, and we will publish our findings in due course.
I’m eligible to get my booster shot. Is there a particular vaccine I should ask for to protect me from Omicron?
The current NHS guidance is that a booster vaccine dose will help improve the protection you have from your first two doses of the vaccine, and help give you longer-term protection against getting seriously ill from COVID-19 – there's more here: https://www.nhs.uk/conditions/coronavirus-covid-19/coronavirus-vaccination/coronavirus-booster-vaccine/
The UK Health Security Agency has published early estimates that of vaccine effectiveness against symptomatic infection against Omicron infection and report a moderate to high vaccine effectiveness of 70-75% is seen in the early period after a booster dose.
Do these data mean that the vaccines no longer work?
Vaccines remain the best protection against COVID-19 and remain highly effective against severe illness and death. There is currently no evidence to suggest that the Omicron variant of COVID-19 results in increased levels of severe illness, or death, amongst those who have received two doses of a vaccine.
The UK Health Security Agency has published early estimates that of vaccine effectiveness against symptomatic infection find it is significantly lower against Omicron infection compared to Delta infection. Nevertheless, a moderate to high vaccine effectiveness of 70-75% is seen in the early period after a booster dose.
What impact, if any, do these data have on current vaccination policies?
The aim of the Joint Committee on Vaccination and Immunisation is to protect those most vulnerable to severe COVID-19. Booster doses are being offered to increase protection for those at highest risk: https://www.nhs.uk/conditions/coronavirus-covid-19/coronavirus-vaccination/
What does this mean for me?
It is important to follow the latest guidance to protect yourself and your family from COVID-19. Vaccines remain the best protection against the virus, along with other public health measures to reduce the risk of becoming infected with COVID-19.
The UK Health Security Agency has published early estimates that of vaccine effectiveness against symptomatic infection against Omicron infection and report a moderate to high vaccine effectiveness of 70-75% is seen in the early period after a booster dose.
