Eurosurveillance - Volume 30, Issue 10, 13 March 2025

Respiratory syncytial virus (RSV) is a major cause of acute respiratory infection that can lead to complications in risk groups.

We aimed to estimate the incidence of RSV hospitalisation in adults, determine the risk factors and characterise priority groups for prevention.

This population-based cohort study included adults 60 years and older in Navarre, Spain, in seasons 2016/17 to 2019/20. We estimated the rate of RSV hospitalisation confirmed by PCR and evaluated risk factors using Poisson regression.

Within 642,622 person-years analysed, we detected 544 RSV hospitalisations (average annual rate: 84.7/100,000). The rate varied among seasons between 59.7 and 95.6 per 100,000. The rate ratio of hospitalisation was higher than 3 from the age of 75 years and around 7 in the 85–94 years age group compared with those aged 60–64 years. Nursing home residence, functional dependence, haematological cancer, chronic obstructive pulmonary disease (COPD), asthma, cardiovascular disease, severe obesity, diabetes and chronic kidney disease were independent risk conditions. Rate of RSV hospitalisation was higher than 300 per 100,000 among people with haematological cancer or nursing home residence, those aged ≥ 75 years with COPD or functional dependence, and those aged ≥ 85 years with asthma or cardiovascular disease. These groups represented 13.2% of all adults aged ≥ 60 years and 50.7% of their RSV hospitalisations. On average, these groups had one RSV hospitalisation per 307 person-years.

Advanced age, in addition to nursing home residence, functional dependence and some comorbidities define priority groups for RSV vaccination.

Evolution of SARS-CoV-2 is continuous.

Between 01/2020 and 02/2022, we studied SARS-CoV-2 variant epidemiology, evolution and association with COVID-19 severity.

In nasopharyngeal swabs of COVID-19 patients (n = 1,762) from France, Italy, Spain, and the Netherlands, SARS-CoV-2 was investigated by reverse transcription-quantitative PCR and whole-genome sequencing, and the virus variant/lineage (NextStrain/Pangolin) was determined. Patients’ demographic and clinical details were recorded. Associations between mild/moderate or severe COVID-19 and SARS-CoV-2 variants and patient characteristics were assessed by logistic regression. Rates and genomic locations of mutations, as well as quasi-species distribution (≥ 2 heterogeneous positions, ≥ 50× coverage) were estimated based on 1,332 high-quality sequences.

Overall, 11 SARS-CoV-2 clades infected 1,762 study patients of median age 59 years (interquartile range (IQR): 45–73), with 52.5% (n = 925) being male. In total, 101 non-synonymous substitutions/insertions correlated with disease prognosis (severe, n = 27; mild-to-moderate, n = 74). Several hotspots (mutation rates ≥ 85%) occurred in Alpha, Delta, and Omicron variants of concern (VOCs) but none in pre-Alpha strains. Four hotspots were retained across all study variants, including spike:D614G. Average number of mutations per open-reading-frame (ORF) increased in the spike gene (average < 5 per genome in January 2020 to > 15 in 2022), but remained stable in ORF1ab, membrane, and nucleocapsid genes. Quasi-species were most prevalent in 20A/EU2 (48.9%), 20E/EU1 (48.6%), 20A (38.8%), and 21K/Omicron (36.1%) infections. Immunocompromised status and age (≥ 60 years), while associated with severe COVID-19 or death irrespective of variant (odds ratio (OR): 1.60–2.25; p ≤ 0.014), did not affect quasi-species’ prevalence (p > 0.05).

Specific mutations correlate with COVID-19 severity. Quasi-species potentially shaping VOCs’ emergence are relevant to consider.

Monoclonal antibodies (mAbs) and antiviral drugs have emerged as additional tools for treatment of COVID-19.

We aimed to review data on susceptibility of 14 SARS-CoV-2 variants to mAbs and antiviral drugs authorised in the European Union/European Economic Area (EU/EEA) countries.

We constructed a literature review compiling 298 publications from four databases: PubMed, Science Direct, LitCovid and BioRxiv/MedRxiv preprint servers. We included publications on nirmatrelvir and ritonavir, remdesivir and tixagevimab and cilgavimab, regdanvimab, casirivimab and imdevimab, and sotrovimab approved by the European Medicines Agency (EMA) by 1 October 2024.

The mutations identified in the open reading frame (ORF)1ab, specifically nsp5:H172Y, nsp5:H172Y and Q189E, nsp5:L50F and E166V and nsp5:L50F, E166A and L167V, led to a decrease in susceptibility to nirmatrelvir and ritonavir, ranging from moderate (25-99) to high reductions (> 100). Casirivimab and imdevimab exhibited highly reduced neutralisation capacity across all Omicron sub-lineages. Sub-lineages BA.1, BA.2 and BA.5 had decreased susceptibility to regdanvimab, while sotrovimab showed decreased efficacy for BA.2, BA.4, BQ.1.1 and BA.2.86. Tixagevimab and cilgavimab exhibited highly reduced neutralisation activity against BQ.1, BQ.1.1, XBB, XBB.1.5 and BA.2.86 sub-lineages.

The emergence of new variants, some with altered antigenic characteristics, may lead to resistance against mAbs and/or antiviral drugs and evasion of immunity induced naturally or by vaccination. This summary of mutations, combination of mutations and SARS-CoV-2 variants linked to reduced susceptibility to mAbs and antiviral drugs, should aid the selection of appropriate treatment strategies and/or phasing out therapies that have lost their effectiveness.