Phase 1 Trial Shows 'Fridge-Free' Tetanus-Diphtheria Vaccine Matches Standard Boosters in Safety and Immunogenicity
核心洞察
A phase 1 trial of SPVX02 (搜索), a room-temperature-stabilised tetanus-diphtheria (搜索) vaccine, demonstrated safety and immunogenicity comparable to two licensed booster vaccines in 60 healthy adults.
The lyophilised vaccine was stored at room temperature for up to a year before reconstitution, potentially eliminating cold-chain dependence that contributes to roughly half of global vaccine wastage.
Experts caution that the 28-day follow-up, small sample size, and 95% white participant population limit generalisability; larger phase 2/3 trials with longer follow-up are needed.
A first-in-human phase 1 trial has demonstrated that SPVX02 (搜索), a room-temperature-stabilised tetanus-diphtheria (搜索) booster vaccine, produces safety and immunogenicity profiles comparable to two established licensed vaccines, raising the prospect of eliminating one of the most persistent barriers to global immunisation: the cold chain.
The multicentre, single-blind, randomised trial, published in eClinicalMedicine, enrolled 60 healthy adults aged 18 to 55 across three UK sites. Participants received either SPVX02 (搜索) — a lyophilised formulation stored at room temperature for up to one year before reconstitution — or one of two licensed comparator vaccines. The results showed that SPVX02 was "safe and well tolerated" and generated "equivalent" immune responses at 28 days post-vaccination, according to Prof Saul Faust, director of the NIHR Clinical Research Facility in Southampton.
The cold-chain problem
Currently, most vaccines require strict temperature control from manufacture to administration — a logistical burden known as the cold chain. The World Health Organization estimates that roughly half of all vaccines globally are wasted each year, with cold-chain failures representing a major contributing factor. Vaccines may be damaged during transport, exposed to temperature excursions, or discarded after passing expiration dates.
"I can remember taking out vaccines in cool boxes… doing that on really inhospitable roads where one couldn't predict getting from A to B in a short period of time and there was always this nervousness about maintaining the cold chain in time to get the vaccines into arms of waiting children," said Prof Saul Faust, reflecting on the real-world challenges the technology aims to address.
The SPVX02 (搜索) formulation, developed by Stablepharma (搜索), converts a liquid tetanus-diphtheria (搜索) vaccine into a dry powder using a stabilisation platform inspired by resurrection plants — organisms that desiccate during drought and revive when water returns. The approach employs the sugar trehalose to preserve vaccine integrity at ambient temperatures.
Trial design and key findings
The phase 1 study randomised 60 volunteers into three groups of 20, each receiving either SPVX02 (搜索) or one of two licensed active comparator vaccines. The trial was not placebo-controlled but used the licensed vaccines as benchmarks for safety and immunogenicity.
The primary findings indicate that room-temperature-stored SPVX02 (搜索) remained safe and immunogenic. However, the study was not powered for formal statistical comparisons between vaccine groups, a limitation noted by multiple independent commentators.
Dr Hamid Merchant, pharmaceutical scientist and Head of Department for Biosciences at the University of East London, observed: "The most important finding is that the vaccine appears to produce safety and immunogenicity profiles similar to existing tetanus-diphtheria (搜索) booster vaccines while potentially removing one of the biggest barriers to global vaccination — the dependence on the cold chain."
Expert cautions and limitations
Despite the encouraging results, several experts urged restraint in interpreting the findings. Prof Linda Klavinskis, Professor of Viral Immunology at King's College London, noted: "The real-world impact claims are a bit premature, since the study only shows immunogenicity at 28 days post vaccination, which is not the same as longer term immune durability i.e. real-world effectiveness. As such, studies with a larger sample size and longer follow-up will be required."
Participant diversity represents another significant limitation. Approximately 95% of trial participants self-identified as white, and all were healthy adults aged 18 to 55. Dr Merchant emphasised that "larger and more representative studies will be needed before the findings can be confidently generalised to wider populations."
Prof Tuck Seng Wong, Professor of Biomanufacturing at the University of Sheffield and Director of the UK-Southeast Asia Vaccine Manufacturing Research Hub, echoed this concern: "If this technology is to help address global health challenges, greater ethnic diversity in clinical evaluation will be important to establish its broader applicability and relevance, particularly in LMIC populations."
Stability claims and unanswered questions
The claim that SPVX02 (搜索) is "unaffected by freezing" derives from laboratory stability and freeze-thaw studies rather than direct clinical evaluation of vaccine exposed to such conditions before administration. Separate data reportedly show the vaccine components survive cycling between -20°C and +40°C, though the clinical trial itself only tested room-temperature-stored material.
Dr Merchant also highlighted gaps in manufacturing transparency: "The paper provides limited detail on how thermostability was achieved, and it remains unclear how the clinical-trial formulation relates to the proprietary sponge-based stabilisation platform described in earlier publications." He added that "an important unanswered question is whether the stability advantage can be delivered through a conventional vaccine-in-a-vial manufacturing process that is sufficiently simple, cost-effective and transferable."
Prof Wong noted that many low- and middle-income countries experience temperatures well above 30°C, as well as substantial day-night temperature fluctuations. "It therefore remains to be seen whether the reformulated and lyophilised vaccine can maintain its stability at higher temperatures and, importantly, whether it is robust enough to withstand significant temperature fluctuations during storage and distribution."
Broader implications
The stabilisation platform appears to be biomolecule-agnostic, suggesting potential applicability beyond tetanus-diphtheria (搜索) vaccines. Prof Wong described this as "where its true value and potential impact lie," noting the strategy could extend to a wide range of biologics. The approach may also be relevant for certain medicines requiring cold storage, such as monoclonal antibodies, though mRNA vaccines cannot currently be adapted using this method.
Because the original tetanus-diphtheria (搜索) vaccine is already approved and licensed, the regulatory pathway for SPVX02 (搜索) does not require the large-scale trials needed for a novel vaccine. The studies are being conducted to meet the WHO's goal of a vaccine that survives at 30°C and 75% relative humidity.
"If those data are positive, the implications could extend well beyond tetanus-diphtheria (搜索) vaccines to other aluminium-adjuvanted vaccines where cold-chain dependence remains a major global challenge," Dr Merchant concluded.