In a recent study posted to the medRxiv* preprint server, researchers determined the immunological landscape of England throughout the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron wave.
During early 2022, determining the extent of the threat presented by the SARS-CoV-2 Omicron (B.1.1.529) variant was a major challenge for public health systems worldwide. Initial studies suggested that although Omicron is more transmissible than the previous SARS-CoV-2 variants, it is associated with less severe forms of coronavirus disease 2019 (COVID-19).
The COVID-19 vaccination rates for those above 12 years were generally high in the United Kingdom (UK). Further, the population of the UK has high levels of infection-imparted immunity from the previous three waves of SARS-CoV-2 during 2020 and 2021.
However, Omicron was associated with a high rate of evasion of immunity provided by previous SARS-CoV-2 infection or vaccination compared to the other SARS-CoV-2 strains. Hence, it is essential to understand the immunological landscape of England in the course of the Omicron-dominated fourth wave of SARS-CoV-2.
About the study
In the current study, the scientists estimated the proportion of individuals with good immunity towards the SARS-CoV-2 B.1.1.529 variant in England. Good immunity was characterized as either two vaccine doses plus a recent booster dose or a recent infection following a two-dose vaccination regimen.
The study population was divided into eight groups consisting of 1) unvaccinated people with no previous exposure to SARS-CoV-2, 2) unvaccinated individuals with a history of SARS-CoV-2, and 3) recipients of one, two, and three SARS-CoV-2 vaccine doses with and without COVID-19 history. In addition, those with a history of SARS-CoV-2 were further divided into those with a recent and nonrecent infection.
The team used an iterative proportional fitting (IPF) process to determine the cell values of a contingency table by employing the estimates of a real-time model infection and national immunization records as marginal values.
Further, the researchers compared the immunological profile during the Omicron-driven wave of COVID-19 in England to the period of the pre-Delta wave, which was before May 2021. The team anticipated that the individuals who received a two-dose vaccine with a prior SARS-CoV-2 infection or a single dose plus a recent COVID-19 history to have significant protection against the Delta variant due to the immunological variations among the Delta and Omicron variants.
Results
The results show that although a high chance of immune evasion was associated with the SARS-CoV-2 Omicron variant, a large fraction of the population in England had significant immunity to the B.1.1.529 strain, especially in the elderly. Nevertheless, since the youngsters were associated with low immunity to the Omicron variant, the endemic SARS-CoV-2 infection might continue for some time.
In detail, while people aged from 45 to 65 years exhibited above 80% immunity against the SARS-CoV-2 B.1.1.529 variant, individuals above 65 years of age demonstrated more than 90% immunity against the Omicron variant with either two vaccine doses plus a recent SARS-CoV-2 infection or three vaccine doses.
However, only around half of the individuals within the 25- and 45-year age groups had received three vaccine doses or had a recent history of COVID-19 plus two vaccine doses. The level of immunity further dropped to nearly 30% in the 15-to-25-year age groups against the Omicron variant. In addition, children exhibited very low immunity against the B.1.1.529 variant.
Furthermore, while the immunity exhibited by people above 75 years during the Omicron infection was similar to the pre-Delta period, the youngsters demonstrated substantial immunity against Omicron relative to the pre-Delta period.
Limitations
The limitations of the study include the following. 1) The IPF analysis used in this investigation was a statistical method without any mechanistic aspects, 2) the study did not consider the disease protection provided by COVID-19 vaccination, 3) past SARS-CoV-2 infections in unvaccinated individuals are probably underestimated, and, 4) time following vaccination was not taken into account as a factor impacting immunity against Omicron.
Conclusions
The study findings demonstrate that the contemporary immunological profile during the Omicron-driven SARS-CoV-2 wave in England was diverse. A significant level of protection against Omicron infection and severe COVID-19 was seen in the older individuals, and as a result, the burden on the healthcare systems was relieved.
Nonetheless, the lower immunity in the younger population against Omicron poses a threat to businesses and other services due to the requirement of self-isolation on testing COVID-19-positive. In addition, since children were associated with very low immunity to Omicron infection, a high chance of uncontrolled spread of Omicron in schools and thereby the risk of community outbreak exists.
Altogether, the present study emphasizes that the younger population is at high risk of Omicron infection in England due to their low immunity against the variant compared to the older age groups. However, since these findings were based on several assumptions of immunity afforded by COVID-19 vaccination and previous SARS-CoV-2 infection against Omicron, further studies are required to adequately measure this immunity and precisely determine population-level protection against Omicron in the UK.
*Important notice
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.
