Implementation of IIF 2022/2023 incentives in England did not lead to any meaningful reduction in overall SABA prescribing but was associated with an almost 4-fold increase in Salamol™ use, reflecting a move away from Ventolin Evohaler™ and generic salbutamol prescribing (a proportion of which is dispensed as Ventolin Evohaler™). While this will have environmental benefits, given the lower carbon impact of Salamol™, the lack of change in SABA prescribing as a whole shows that SABA over-use was not tackled at scale. This suggests that incentive schemes, such as the IIF, maybe sufficient to bring about apparently simple changes in prescribing practice (between brand prescription changes), albeit with potential to promote scaled prescription switching. However, the lack of impact on overall SABA prescribing suggests that incentives alone may not be sufficient to achieve more complex changes in care, such as addressing SABA over-use.

In contrast, SENTINEL Plus early adopter sites achieved a significant reduction in SABA prescribing in the period after SENTINEL Plus implementation, confirming its ability to support clinical practice change across diverse primary care sites in England. Electronic health record data from >2500 asthma patients in the SENTINEL Project pilot PCN demonstrated similar prescribing changes and a reduction in asthma exacerbations post-implementation11, supporting an assumption that the observed prescribing changes will translate into patient benefit.

Significantly lower reductions in SABA prescribing were observed among early adopter practices that appeared to have also engaged in a SABA switch programme. Many factors may influence this observation, and it is not possible to conclude cause and effect based on the presented data. However, it is important to consider whether incentives to promote lower carbon SABA inhaler use may have adversely affected efforts to tackle SABA over-use as a whole. Indeed, addressing SABA over-use in asthma is challenging due to the complex and often numerous contributory patient, clinician, and health system factors12,13. Changing both clinician and patient behaviour is vital and clear messaging about the harms of SABA over-use in asthma is essential. This may be undermined by concurrent efforts to promote an alternative, less environmentally harmful SABA. Something that will continue to be relevant with the advent of new propellant gasses that will lower the environmental impact further14.

The nature and weighting of IIF Target ES-025 also meant that a practice that significantly reduced their overall SABA prescribing but did not lower the mean carbon footprint per SABA, would have received less funding through the IIF than a practice that increased overall SABA prescribing, but did so using lower carbon inhalers. This is despite the former scenario having greater patient and environmental benefit.

For 2023/2024, the IIF has changed to focus on healthcare access, with loss of specific incentives to transform asthma care. This is leading local healthcare commissioners to consider introducing bespoke prescribing targets for their regions to continue to drive improvements aligned to the NHS long-term plan. It is therefore timely to consider whether greater synergy between patient and environmentally focussed incentives could be achieved by i) recognising the carbon savings from reduced overall SABA prescribing in asthma and ii) balancing financial incentives to prioritise patient benefit. While incentives alone may not be sufficient to overcome complex healthcare challenges, they have an important role in supporting practice change and should be considered alongside quality improvement packages to maximise impact. We would therefore strongly support reintroduction of RESP-02 but with aligned implementation support using a quality improvement package such as SENTINEL Plus.

When considering the implications of our findings, it is important to acknowledge the limitations of this study. Openprescribing.net data includes all primary care prescriptions and therefore captures prescribing for other respiratory conditions, such as COPD, in addition to asthma. This is less of a limitation when considering measures that span conditions, such as ES-02, but would be expected to limit the ability to detect change among specific sub-groups within the whole population, such as adult asthma patients that over-use SABA, the focus of SENTINEL Plus. Despite this, we observed a significant reduction in SABA and increase in ICS prescribing among early adopter sites, indicating the ability to detect changes in asthma prescribing using population-level data. Another limitation is the absence of matched controls for our SENTINEL Plus early adopter sites, raising the potential that factors other than the intervention may have impacted prescribing. However, analysis of national prescribing data did not reveal any significant change in SABA prescribing at a population level, increasing the likelihood that the change in prescribing observed post-SENTINEL Plus implementation is a consequence of the intervention, rather than a wider trend. Findings from the SENTINEL Project pilot site also support the interventions effectiveness11.

When complete, the full SENTINEL Project effectiveness evaluation will provide definitive evidence about the impact of the SENTINEL intervention on prescribing, clinical outcomes and the environmental impact of asthma care. An associated implementation evaluation will provide insights into barriers and facilitators to successful implementation. However, while this is awaited, we present promising data from early SENTINEL Plus adopting practices and suggest that concurrent programmes to switch higher carbon to lower carbon SABA inhalers at scale have potential to negatively impact efforts to overcome SABA over-use as a whole and should be approached with care.

In conclusion, total SABA prescribing in England remained unchanged during the 12-months following IIF 2022/2023 introduction but there was a significant shift to use of lower carbon impact SABA inhalers. SENTINEL Plus implementation within primary care practices in England was associated with a significant reduction in total SABA prescribing; but, practices that undertook additional SABA switch programmes were less likely to achieve these overall reductions. It is therefore important for policy makers to develop incentives that act synergistically to achieve the desired practice change. To tackle SABA over-use at scale, consideration should be given to aligning incentives with quality improvement interventions.