Boosters Critical To Mitigate Omicron Impact, But May Lose Effect | Imperial News

Levels of neutralizing antibodies to prevent infection with Omicron have been reduced and the vaccine’s effectiveness against serious illness is expected to drop, according to a new report.

Vaccines have played a central role in mitigating serious illness and death from COVID-19 over the past 12 months. However, the emergence of worrisome variants has resulted in loss of vaccine efficacy against mild infections and subsequent transmission. While the magnitude of the decline in critical illness (ie.

Vaccine efficacy

In this latest report from the Imperial College COVID-19 response team, researchers adapted an immunologic model to population-level vaccine efficacy data to determine vaccine efficacy against the variant. Omicron.

Our estimates suggest that this is likely to result in small but significant reductions in effectiveness against serious illness and death. Prof. Azra Ghani

After two initial doses and a booster vaccine with an mRNA vaccine (Pfizer BioNTech or Moderna), neutralizing antibodies (which prevent infection) should increase 1.6-fold (95% credibility interval, CrI 1.4 at 1.9) compared to the levels after dose 2 of the Pfizer-BioNTech vaccine and 3.3 times (95% CrI 2.5-4.7) compared to their levels after dose 2 of the Oxford-AstraZeneca vaccine. However, the researchers estimate that when the immune system encounters a variant, the levels of neutralizing antibodies produced against Omicron could be 4.5 times (95% CrI 3.1-7.1) lower than those produced against the Delta variant.

Crucial booster doses

The researchers are also finding that this reduction in neutralizing antibodies could impact the vaccine’s effectiveness against serious disease. In the worst-case scenario where the rate of decay after a booster dose is the same as that seen after the first 2 doses, the study predicts that the efficacy of the vaccine against serious illness (hospitalization) could drop by 96.5 % (95% CrI 96.1% – 96.8%) against Delta at 80.1% (76.3% –83.02) against Omicron 60 days after the primary vaccination followed by a booster of the Pfizer-BioNTech vaccine if the antibodies degrade at the same rate after the booster as that observed after the course primary vaccination. If this rate of decrease is half of this rate, the decrease is estimated at 97.6% (95% CrI 97.4% -97.9%) against Delta at 85.9% (95% CrI 83.1% -88.3%) against Omicron. However, this could be even more moderated by the increased longevity of T cell-mediated immunity.

The researchers say that while these numbers are currently associated with a high degree of uncertainty, they indicate that Omicron variant-specific vaccines and / or additional boosters are likely to be needed to restore protection.

Global vaccine distribution

The report integrates this immunological model with a model of transmission of the SARS-CoV-2 virus to examine how booster doses should best be deployed given the current state of the global pandemic. The researchers model three scenarios – one for countries with significant past transmission (and infection-induced immunity) and high level of access to vaccines, one for countries with significant past transmission but limited access to vaccines. vaccines, and one for so-called “zero-COVID” countries with limited past transmission.

Boosters will be a key part of the policy response to reduce hospitalizations and deaths and prevent health systems from being overburdened. Dr Alexandra Hogan

Their results demonstrate that the booster doses will be essential to mitigate the impact of future Omicron waves in countries with high levels of circulating viruses.

Booster doses will also be needed in “zero-COVID” countries to prevent further waves of infection and to open safely.

When vaccine supply is limited or vaccine deployment is delayed, it is more beneficial to target booster doses to the groups most at risk to ensure high and continued protection in the face of declining immunity than to give these doses as a primary vaccination to younger age groups.

The researchers note that we still don’t know how severe the disease caused by the Omicron variant is compared to the disease caused by the previous variants.

Prof. Azra Ghani of Imperial College London said: “Given the rapid spread of the Omicron variant to date, it is now very likely that it will replace the Delta variant circulating around the world in the coming weeks. Emerging immunogenicity data clearly indicate substantial reductions in neutralizing antibodies, while preliminary estimates of vaccine efficacy demonstrate a substantial reduction in protection against mild disease. Our estimates suggest that this is likely to result in small but significant reductions in effectiveness against serious illness and death. One remaining uncertainty is the severity of illness caused by the Omicron variant compared to illness caused by previous variants. While it may take several weeks to fully understand this, governments will need to put plans in place now to mitigate any potential impact. Our results demonstrate the importance of administering booster doses as part of a broader public health response. Prioritizing such booster shots in high-risk populations rather than primary immunization in younger age groups should be part of this response in countries where dose supply is limited.

Dr Alexandra Hogan of Imperial College London said: “Although the data is still emerging, the rapid spread of the Omicron variant is of great concern. Substantial increases in infections and cases are expected in the coming weeks, both in countries where the virus is circulating, and in settings that have previously suppressed transmission and are now lifting restrictions. Our study provides further evidence of the importance of giving booster doses as an immediate priority, especially in older, high-risk, and priority populations. While we do not yet fully understand the implications of Omicron in terms of disease severity, boosters will be a key part of the policy response to reduce hospitalizations and deaths, and to prevent healthcare systems from becoming overburdened. “

The work, which has not yet been peer-reviewed, is presented in the latest report from the WHO Collaborating Center for Infectious Disease Modeling at the MRC Center for Global Infectious Disease Analysis, Jameel Institute, Imperial College London.

Since the emergence of the novel coronavirus (COVID-19) in December 2019, the COVID-19 response team at Imperial College has adopted a policy of immediately sharing research results on the developing pandemic.