Miss the winter wave, and you wait a year

The problem

Host-response assays measure the patient’s immune response to infection rather than the pathogen itself.² Specimens have to be drawn from patients presenting with acute febrile illness, inside a short symptom-onset window, while the host-response signal is still measurable.

That makes enrollment a function of how many febrile patients walk through an outpatient door — and that is a quantity set by the season, not by the program. Acute-respiratory presentations concentrate in a wave running from late November through January. The program had exactly one wave available to it.

What made it hard

The season sets the ceiling

Acute-respiratory volume at outpatient sites concentrates post-Thanksgiving through January. A program that misses that window cannot make the volume up with coordinator effort. It waits a year.
The symptom-onset window is short

Specimens must be drawn within days of symptom onset. Consent and draw had to happen in the same visit, or the subject aged out of eligibility before the specimen was taken.
Comparator testing had to ride along

Each subject needed paired pathogen testing so the sponsor could later classify assay performance against documented pathogen status. That had to come from the routine clinical work-up, without adding a second visit.

62% of program volume arrived in December. That is not a scheduling failure — it is the shape of the disease.

What we did

Reused three sites we already knew

All three sites were partners from earlier host-response programs. Qualification, contracting, and IRB submission were already done — roughly 6–8 weeks of start-up that a new network would have cost. That saving is the entire reason an October activation was possible.

Consent and draw in a single visit

Coordinators identified eligible subjects at urgent-care intake, verified symptom onset at consent, and collected the specimen alongside the routine clinical work-up. Consent-to-draw stayed under an hour, so the multi-visit attrition that normally erodes these studies never had a chance to occur.

Activated in October, deliberately

October (+16) and November (+30) were coordinator ramp. December (+97) was the wave. January (+14) was the tail. The activation date was chosen against the seasonal calendar, not against internal readiness.

New-site-network frame (alternative)

Site qualification, master contracting, IRB submission, site-initiation visits at unfamiliar sites. ~6–8 weeks of program-front overhead. Risk of activating outside the seasonal window.

Existing-partner frame (this program)

Three sites from prior host-response engagements with the same RDI operational spine. Site qualification, contracting, and IRB overhead eliminated. October activation aligned to capture the post-Thanksgiving acute-respiratory wave at full coordinator throughput.

What happened

Enrollment reached 157 at close in January 2025 — 16 by end-October, 46 by end-November, 143 by end-December, then a 14-subject tail (Fig. 1). December alone carried 62% of the program.

Site A took 82 subjects (52%), Site B 57 (36%), and Site C 18 (11%) (Table 1; Fig. 2). The split tracks each site’s underlying acute-respiratory patient volume rather than any difference in coordinator performance.

Oct 2024 Activation / +16

Nov 2024 Coordinator ramp / +30

Dec 2024 Seasonal peak (+97)

Late Dec 2024 Post-Thanksgiving wave running

Jan 2025 Tail / +14

End-Jan 2025 Program close (157)

Table 1 Site-level enrollment across the 4-month program window. All three sites are existing partners from prior host-response engagements at the same RDI operational spine; site qualification overhead was eliminated through partnership reuse.
Site	Setting	Enrolled	Share
Site A	Urgent-care / family-medicine clinic; established outpatient febrile-illness flow	82	52%
Site B	Multi-specialty clinic with established outpatient febrile-illness flow	57	36%
Site C	Urgent-care / family-medicine clinic; smaller acute-respiratory patient volume	18	11%
All sites at program close (Jan 2025)	3 outpatient/urgent-care sites; 4-month enrollment window	157	100%

Fig. 1 Cumulative enrollment (orange line) and monthly enrollment (gray bars) across the 4-month program window. The +97 December peak reflects the post-Thanksgiving acute-respiratory illness wave running through the three sites at full coordinator throughput; the structural cadence is set by seasonal incidence of acute-respiratory illness, not by site capacity. Approximately 62% of program volume delivered in a single month. Source: RDI Salesforce enrollment dashboard at program close, January 2025.

Fig. 2 Site contribution at program close. The two lead sites (A and B) carried 88% of program volume between them; Site C contributed at lower volume reflecting smaller underlying acute-respiratory patient flow. Source: RDI Salesforce enrollment dashboard at program close, January 2025.

What transfers

Programs in acute febrile illness should be judged on seasonal-window throughput, not monthly smoothness. A flat enrollment curve is not achievable when the underlying clinical syndrome is not flat, and a program manager who chases one is optimising for the wrong thing.

Two things follow. Activation timing is a design decision, not a scheduling detail — the calendar decides whether the wave is available at all. And where a sponsor has run with us before, reusing qualified sites is the cheapest way to buy activation speed. Here it was the difference between catching the December wave and missing it entirely.

Notes

Sponsor identity withheld per confidentiality terms. Protocol code, target counts, marker panel, and assay platform names omitted. The sponsor descriptor reflects the sponsor’s category.
Host-response assays measure markers of the patient’s immune response — typically combinations of viral- and bacterial-induced cytokines. Several assays in this category hold FDA clearances.
Site labels are anonymised. Counts (157 subjects; +97 December peak; ~62% single-month share) are taken from the RDI enrollment dashboard at program close, January 2025.
No human-subjects data, identifiers, or laboratory results are reported. This is an operations report, not a clinical-results publication.

Suggested citation. RDI Trials. Miss the winter wave, and you wait a year. RDI Trials & Operations Reports, 2026;14. RDItrials.com.

In short