A new COVID-19 subvariant, XBB.1.5, has been detected in 29 other countries worldwide, the World Health Organization (WHO) reported.

XBB.1.5, which is another descendant of the Omicron variant, is “the most transmissible subvariant that has been detected yet”, WHO COVID-19 technical lead, Maria Van Kerkhove, said at a press conference this month.

The reason for this is because of the mutations XBB.1.5 contains, allowing it to adhere to cells and replicate easily.

WHO said it does not yet have any data on the severity of XBB.1.5, but currently has no indication that this would have increased.

XBB.1.5 is causing concern in the US, where it has been spreading rapidly since December 2022. Data from the US Centers for Disease Control and Prevention (CDC) has estimated that XBB and XBB.1.5 accounted for 44.1% of US COVID-19 cases in the week of 31 December, compared to 25.9% in the previous week.

WHO’S Technical Advisory Group on Virus Evolution, which meets regularly to review the latest scientific evidence on circulating SARS-CoV-2 variants and advises WHO on whether a change in public health strategies is warranted, is evaluating the rapidly increasing proportion of XBB.1.5 in the US and other countries.

The World Health Organization (WHO) has updated its COVID-19 guidelines on treatments, isolation periods and mask wearing.

Included in the advice is a strong recommendation for the use of Pfizer’s Paxlovid (nirmatrelvir/ritonavir) in COVID-19 patients who are at high risk of hospitalisation.

WHO also reviewed the evidence on two other medicines, GSK/Vir Biotechnology’s Xevudy (sotrovimab) and Regeneron/Roche’s REGEN-COV (casirivimab/imdevimab), and maintains strong recommendations against their use for treating COVID-19.

The guidelines also recommend a reduced isolation period, with WHO advising that COVID-19 patients can be discharged from isolation early if they test negative on an antigen-based rapid test.

Without testing, for patients with symptoms, the new guidance suggests ten days of isolation from the date of symptom onset. Previously, WHO advised that patients be discharged ten days after symptom onset, plus at least three days since symptoms’ resolution.

Additionally, for those who test positive for COVID-19 but do not have any signs or symptoms, WHO now suggests five days of isolation in the absence of testing, compared to a previous ten days.

The use of masks by the public in specific situations has also been recommended in the update, irrespective of the local epidemiological situation, which is previously what WHO’s recommendations were based on.

GSK and CureVac will be advancing their jointly developed mRNA COVID-19 and flu vaccine candidates to the next stage of clinical testing after announcing positive preliminary results from early stage trials.

The tested vaccine candidates produced promising immunogenicity and reactogenicity profiles in ongoing phase 1 clinical programmes for COVID-19 and seasonal flu, assessing both modified and unmodified mRNA technology.

Each clinical programme assessed the vaccine candidates based on CureVac’s second-generation mRNA backbone to ‘achieve improved mRNA translation and strong immune responses at low doses’, the company explained.

While the COVID-19 programme tested two monovalent candidates, the flu programme included an unmodified multivalent and a modified monovalent vaccine.

The monovalent modified mRNA COVID-19 vaccine candidate CV0501, encoding Omicron variant BA.1, was shown to successfully boost antibody levels against BA.1 and ancestral variants in healthy adults and was generally well tolerated across all tested dose groups.

The monovalent modified mRNA flu vaccine candidate Flu-SV-mRNA also successfully boosted antibody levels against matching flu strain and was well tolerated across all tested dose groups.

The companies plan to start the second phase of their COVID-19 clinical programme later this year, while a seasonal flu study to target four different strains should begin towards the middle of the year.

AstraZeneca’s (AZ) phase 1/3 SUPERNOVA trial has commenced, with the first of RQ Bio’s discovered monoclonal antibodies (mAbs) to prevent COVID-19 in vulnerable patients entering the study less than 12 months after discovery.

The start of the trial triggers a $5m milestone payment from AZ, which licensed AZD3152 from RQ Bio in May last year, and reinforces the financial position of the UK-based biotech to execute its four scientific programmes focused on viral diseases.

AZ’s trial will evaluate the safety and neutralising activity of AZD5156 – a combination of AZD3152 and cilgavimab – for the prevention of COVID-19 in patients with conditions that cause immune impairment and who are therefore less likely to build an adequate response through vaccination.

An accelerated development programme by AZ means a new COVID-19 treatment could become available in the second half of 2023, RQ Bio said, subject to trial read-outs and regulatory reviews.

The launch of RQ Bio was announced in May last year, following the completion of the licensing deal with AZ.

Under the terms of the agreement, AZ was granted an exclusive worldwide licence to develop, manufacture and commercialise the company’s existing early stage mAbs for SARS-CoV-2, with RQ Bio eligible for milestone payments of up to $157m, plus royalties.

Novavax has announced the initiation of a phase 2 trial for its combination COVID-19/influenza and stand-alone influenza vaccine candidates.

The trial will evaluate the safety and effectiveness of different formulations of the company’s recombinant protein-based COVID-19 vaccine, quadrivalent influenza vaccine candidate and patented saponin-based Matrix-M adjuvant in adults aged 50 to 80 years.

Initial results from the trial, which is expected to enrol around 2,300 participants across sites in Australia and New Zealand, are expected towards the middle of the year. This data will inform the phase 3 trials for both influenza stand-alone and COVID-19/influenza combination candidates, the company said.

Novavax announced positive phase 1/2 results for its combination COVID-19/influenza vaccine candidate in October 2022, which demonstrated the vaccine’s ability to generate immune responses against SARS-CoV-2 and homologous and heterologous influenza strains.

Using a combined vaccine approach has the potential to alleviate the impact of both viruses while offering a combined administration, potentially simplifying immunisation practices for healthcare providers and leading to higher vaccine uptake.

In November 2022, Pfizer and BioNTech also initiated a phase 1 study of their mRNA-based combination COVID-19/influenza vaccine.

The vaccine combines Pfizer’s quadrivalent modified RNA-based influenza vaccine candidate, currently in phase 3 clinical development, and the Pfizer/BioNTech-authorised Omicron-adapted bivalent COVID-19 vaccine.