Clover Announces Additional Positive U.S. Phase I Clinical Data for RSV Re-Vaccination in Older Adults

-- Additional data from RSV re-vaccination trial demonstrates trend of approximately 60-80% higher RSV neutralizing antibodies (nAbs) for Clover's RSV vaccine compared head-to-head versus AREXVY (GSK) in older adults who previously received an initial dose of AREXVY --

-- Re-vaccination with Clover's RSV vaccine boosted RSV nAbs to approximately 120-135% of the peak levels observed after an initial dose of AREXVY (cross-trial comparison) --

-- Results further strengthen profile of potential best-in-class RSV+hMPV±PIV3 combination vaccines, with the potential ability to re-vaccinate individuals previously receiving approved RSV vaccines to restore and broaden protection --

SHANGHAI, March 24, 2026 /PRNewswire/ -- Clover Biopharmaceuticals, Ltd. (Clover; HKEX: 02197), a global commercial-stage biotechnology company committed to unleashing the power of innovative vaccines to save lives and improve health around the world, today announced additional positive data from a Phase I clinical trial in the U.S. evaluating re-vaccination with the company's RSV PreF vaccine candidate (SCB-1019) compared head-to-head versus GSK's RSV vaccine (AREXVY) in older adults that previously received AREXVY at least 2 seasons prior to enrolling. The results announced today are from 62 participants, whereas the results announced in October 2025 were from 34 participants.

"These additional clinical data in nearly double the number of subjects compared to the prior analysis re-affirm our differentiated ability to re-vaccinate older adults previously receiving an approved RSV vaccine, further strengthening the potential best-in-class profile for our RSV+hMPV±PIV3 combination vaccine candidates," said Joshua Liang, Chief Executive Officer & Board Director of Clover. "While currently approved protein-based RSV vaccines are safe & effective, critical gaps persist globally, including (1) the inability to prevent significant respiratory disease burden caused by other viruses related to RSV such as human metapneumovirus (hMPV) and parainfluenza virus type 3 (PIV3) and (2) the inability to re-vaccinate effectively when protection against RSV disease wanes. Enrollment in the Phase II clinical trial for our RSV+hMPV±PIV3 combination vaccines remains ongoing." 

The Phase I trial in the U.S. enrolled older adults (60-85 years) who previously received an initial dose of GSK's RSV vaccine (AREXVY) at least 2 seasons prior. Participants were randomized to receive either a heterologous SCB-1019 (Clover RSV PreF) revaccination dose, a homologous AREXVY (GSK RSV PreF) revaccination dose or saline placebo. The study is assessing safety, reactogenicity and immunogenicity.

An analysis for immunogenicity in all enrolled participants has been performed. Preliminary and exploratory results from 62 participants (30 participants receiving SCB-1019, 26 participants receiving AREXVY, 6 participants receiving saline placebo) are summarized below:

• SCB-1019 heterologous re-vaccination induced an approximately 60-80% higher trend in RSV-A and RSV-B nAb geometric mean titers (GMTs) compared to AREXVY homologous re-vaccination; no significant changes in RSV nAbs were observed for the placebo group

• An exploratory cross-trial comparison to sera from Clover's prior clinical study in RSV vaccine-naïve older adults receiving an initial dose of AREXVY suggests that SCB-1019 heterologous re-vaccination restores RSV-A and RSV-B nAb GMTs to approximately 120-135% of peak levels observed following an initial dose of AREXVY, whereas AREXVY heterologous re-vaccination restored GMTs to only approximately 75% of peak levels

• AREXVY homologous re-vaccination induced an approximately 40-fold increase in "off-target" antibodies against the T4-foldon trimerization tag utilized in AREXVY

Given that more than 40% of eligible adults 60 years and older in the U.S. have previously received a protein-based RSV vaccine (comprising approximately 15 million doses)^[1], and clinical data to-date for currently approved RSV vaccines have not supported RSV re-vaccination policy recommendations despite waning efficacy observed after the initial dose, Clover's clinical data to-date suggest the potential for Clover's RSV+hMPV±PIV3 combination vaccine candidates to both restore protection against RSV and broaden protection to hMPV±PIV3 in this population.

Clover's RSV+hMPV±PIV3 combination vaccine candidates are currently being evaluated in an ongoing Phase II clinical trial that initiated enrollment in January 2026.

About Clover 

Clover Biopharmaceuticals is a global commercial-stage biotechnology company committed to unleashing the power of innovative vaccines to save lives and improve health around the world. With integrated research and development, manufacturing and commercial capabilities as well as strong partnerships with organizations globally, Clover has a diverse pipeline of candidates that have the potential to meaningfully reduce the burden of vaccine-preventable diseases—and to make more diseases preventable.   

Clover Forward-looking Statements  

This press release contains certain forward-looking statements and information relating to us and our subsidiaries that are based on the beliefs of our management as well as assumptions made by and information currently available to our management. When used, the words "aim," "anticipate," "believe," "could," "estimate," "expect," "going forward," "intend," "may," "might," "ought to," "plan," "potential," "predict," "project," "seek," "should," "will," "would" and the negative of these words and other similar expressions, as they relate to us or our management, are intended to identify forward-looking statements.   Forward-looking statements are based on our current expectations and assumptions regarding our business, the economy and other future conditions. We give no assurance that these expectations and assumptions will prove to have been correct. Because forward-looking statements relate to the future, they are participant to inherent uncertainties, risks and changes in circumstances that are difficult to predict. Our results may differ materially from those contemplated by the forward-looking statements. They are neither statements of historical fact nor guarantees or assurances of future performance. We caution you therefore against placing undue reliance on any of these forward-looking statements. Any forward-looking statement made by us in this document speaks only as of the date on which it is made. Factors or events that could cause our actual results to differ may emerge from time to time.

SOURCE Clover Biopharma