Deleted: Global experts have warned that Omicron BA.5, the coronavirus strain currently outpacing other variants in infection and the dominant strain in most countries, is able to re-infect people within weeks of contracting the virus.
Andrew Roberston, chief health officer in Western Australia, said though previously it was believed that most people would retain a certain level of protection against re-infection if they were vaccinated or had retained some level of natural immunity due to a recent contraction of the virus, this isn’t the case with the most recent strain.
“We are seeing more and more people who have been infected with BA.2 and then becoming infected after four weeks,” he said in an interview with the News.com Australian news outlet. “So maybe six to eight weeks later they are developing a second infection, and that’s almost certainly BA.4 or BA.5.”
The ability for strains BA.4 and BA.5 to re-infect individuals who would in previous waves of COVID-19 had stronger immunity has experts calling this latest strain the most transmissible yet, reports The Independent.
In the US, BA.5 has now taken over as the dominant strain, accounting for 88.8% of cases. And though the average number of new cases recorded daily in the country is currently around 112 000, experts fear a combination of home testers not reporting positive cases, a closure of government-funded testing centres and an increasing number of states stopping their daily data updates, has led to a less accurate picture of how much this new strain is actually penetrating the nation.
A recent British study published in Science has confirmed the troubling reality that many may have already been experiencing anecdotally with multiple back-to-back reinfections: these two new subvariants evade protection from previous infections and vaccines.
Immunology professor Danny Altmann, co-author of the Science paper with Rosemary Boyton, a professor of immunology and respiratory medicine, said contrary to a popular held belief that vaccines and previous infection would provide “a wall of immunity”, nations are instead experiencing “wave after wave of new cases”.
In the study, Altmann said they followed individuals who were triple vaccinated and those who suffered breakthrough infections during earlier Omicron waves. “This lets us examine whether Omicron was, as some hoped, a benign natural booster of our COVID immunity,” he said, but “it turns out that isn’t the case”.
Most people, even when triple-vaccinated, had 20 times less neutralising antibody response against Omicron than against the initial ‘Wuhan’ strain.
Altmann said Omicron infection was a poor booster of immunity to further Omicron infections. “It is a kind of stealth virus that gets in under the radar,” he said, and “even having had Omicron, we’re not well protected from further infections”.
The US Federal Drug Administration (FDA) has recommended that COVID vaccine makers, namely Pfizer and Moderna, begin modifying what they have on offer so that their booster shots can more accurately target the BA.4 and BA.5 variants and estimated that these shots could become available as early as mid-fall.
Study details
Immune boosting by B.1.1.529 (Omicron) depends on previous SARS-CoV-2 exposure
Catherine Reynolds, Corinna Pade, Joseph Gibbons, Ashley Otter, Kai-Min Lin, Diana Sandoval, Franziska Pieper, David Butler, Siyi Liu, Rosemary Boyton et al
Published in Science on 14 June 2022
Abstract
Introduction
B.1.1.529 (Omicron) and its subvariants pose new challenges for control of the COVID-19 pandemic. Although vaccinated populations are relatively protected from severe disease and death, countries with high vaccine uptake are experiencing substantial caseloads with breakthrough infection and frequent reinfection.
Rationale
We analysed cross-protective immunity against B.1.1.529 (Omicron) in triple-vaccinated health care workers (HCWs) with different immune-imprinted histories of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection during the ancestral Wuhan Hu-1, B.1.1.7 (Alpha), and B.1.617.2 (Delta) waves and after infection during the B.1.1.529 (Omicron) wave in previously infection-naïve individuals and those with hybrid immunity, to investigate whether B.1.1.529 (Omicron) infection could further boost adaptive immunity. Spike subunit 1 (S1) receptor binding domain (RBD) and whole spike binding, live virus neutralising antibody (nAb) potency, memory B cell (MBC) frequency, and T cell responses against peptide pools and naturally processed antigen were assessed.
Results
B and T cell recognition and nAb potency were boosted against previous variants of concern (VOCs) in triple-vaccinated HCWs, but this enhanced immunity was attenuated against B.1.1.529 (Omicron) itself. Furthermore, immune imprinting after B.1.1.7 (Alpha) infection resulted in reduced durability of antibody binding against B.1.1.529 (Omicron), and S1 RBD and whole spike VOC binding correlated poorly with live virus nAb potency. Half of triple-vaccinated HCWs showed no T cell response to B.1.1.529 (Omicron) S1 processed antigen, and all showed reduced responses to the B.1.1.529 (Omicron) peptide pool, irrespective of SARS-CoV-2 infection history. Mapping T cell immunity in class II human leukocyte antigen transgenics showed that individual spike mutations could result in loss or gain of T cell epitope recognition, with changes to T cell effector and regulatory programs. Triple-vaccinated, previously infection-naïve individuals infected during the B.1.1.529 (Omicron) wave showed boosted cross-reactive S1 RBD and whole spike binding, live virus nAb potency, and T cell immunity against previous VOCs but less so against B.1.1.529 (Omicron) itself. Immune imprinting from prior Wuhan Hu-1 infection abrogated any enhanced cross-reactive antibody binding, T cell recognition, MBC frequency, or nAb potency after B.1.1.529 (Omicron) infection.
Conclusion
Vaccine boosting results in distinct, imprinted patterns of hybrid immunity with different combinations of SARS-CoV-2 infection and vaccination. Immune protection is boosted by B.1.1.529 (Omicron) infection in the triple-vaccinated, previously infection-naïve individuals, but this boosting is lost with prior Wuhan Hu-1 imprinting. This “hybrid immune damping” indicates substantial subversion of immune recognition and differential modulation through immune imprinting and may be the reason why the B.1.1.529 (Omicron) wave has been characterised by breakthrough infection and frequent reinfection with relatively preserved protection against severe disease in triple-vaccinated individuals.
Independent article – ‘Stealthy’ new Covid variant can reinfect you every month (Open access)
See more from MedicalBrief archives:
COVID sub-variant spreads and new symptoms emerge
NICD statistics: COVID cases rise as two Omicron sub-lineages spread across SA
European warning that two strains of Omicron from SA are ‘variants of concern’