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The following is a summary of “Dynamics of SARS-CoV-2 variants and mutations in Central Sweden between 2023 and 2024 and their potential implications on monoclonal antibodies pemivibart and sipavibart as PrEP in the region,” published in the May 2025 issue of Infectious Diseases by Haars et al. 

Monoclonal antibodies (mAbs), including sipavibart and pemivibart, had been used as pre-exposure prophylaxis (PrEP) for individuals with immune system impairment, although certain SARS-CoV-2 variants carried spike (S) protein mutations that reduced their effectiveness. These therapies were particularly relevant during times of heightened transmission or public health emergency when rapid protection for vulnerable populations was critical. 

Researchers conducted a retrospective study to examine the relative abundance of circulating SARS-CoV-2 variants and mutations in central Sweden between 2023 and 2024 and to predict the effectiveness of sipavibart and pemivibart. 

They applied an amplicon-based Nanopore sequencing approach to analyze SARS-CoV-2 samples. Coronapp was used to detect mutations in the sequences obtained. The effectiveness of sipavibart and pemivibart was inferred using published in vitro resistance data. 

The results showed a rise in the relative abundance of the KP.3.1.1 variant and the Q493E mutation in late 2024. Since April 2024, the F456L mutation reached 100% relative abundance for several weeks until the study ended. The KP.3.1.1 variant demonstrated significant resistance to pemivibart. The F456L mutation, found in Omicron subvariants, conferred high fold resistance toward sipavibart. 

Investigators concluded that using sipavibart or pemivibart as PrEP for COVID-19 had likely been ineffective in the region due to resistance mutations, highlighting the value of routine sequencing to guide future mAb use, especially in emergency settings involving rapidly evolving viral threats. 

Source: tandfonline.com/doi/full/10.1080/23744235.2025.2509011#abstract