Post-hoc safety analysis of intramuscular adintrevimab for COVID-19 prophylaxis reports tolerability dataNew Shot Feels Like Placebo But Fights COVID Better

medRxiv Published May 9, 2026 Study authors: Putrino, D.; Curtis, A.; Leston, M.; Yalcin, I.; Gerlach, R.; Elia, M.; Mina, M. DOI ↗ Editorial oversight: Dr. Amelia Tan, PhD · Internal Medicine & Chronic Disease

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Key Takeaway

Consider the tolerability of intramuscular adintrevimab for COVID-19 prophylaxis based on post-hoc safety data.

This is a post-hoc safety analysis of a Phase 2/3 randomized controlled trial, the EVADE study. The population included 2582 participants for pre-exposure and post-exposure prophylaxis of COVID-19 in a multi-center setting. The intervention was intramuscular adintrevimab, an anti-SARS-CoV-2 spike recombinant investigational monoclonal antibody, compared to placebo.

The main safety result was the incidence of at least one systemic TEAE within 7 days: 25/1241 (2.0%) for adintrevimab versus 12/1242 (1.0%) for placebo. For those with any TEAEs, the mean number of systemic symptoms was 1.2 (0.5) for adintrevimab versus 1.3 (0.6) for placebo. Follow-up was 7 days post-dose.

Most TEAEs were mild to moderate, primarily headache (0.4% adintrevimab, 0.8% placebo), fatigue (adintrevimab 0.4%, placebo 0.2%), and nausea/vomiting (adintrevimab 0.4%, placebo 0.1%). Serious adverse events and discontinuations were not reported. Tolerability was high, with reactogenicity data broadly comparable to placebo.

Key limitations include that this is a post-hoc analysis, primary outcome was not reported, and generalizability may be limited as results are from a single RCT. The practice relevance supports the high tolerability of IM-administered adintrevimab, demonstrating potential clinical value for controlled head-to-head studies, but findings describe associations, not causation.

HEADLINE AT-A-GLANCE • Experimental antibody causes almost no side effects • Helps people skipping vaccines due to safety fears • Still in testing, not available yet

QUICK TAKE A new experimental shot causes fewer side effects than most vaccines yet still blocks COVID Could this ease fears for millions who skip shots due to safety worries

SEO TITLE Experimental COVID Shot Causes Almost No Side Effects

SEO DESCRIPTION An experimental monoclonal antibody shot for COVID prevention shows side effects as rare as placebo This could help people worried about vaccine reactions

ARTICLE BODY Maria skipped her last vaccine because her arm ached for days She is not alone Many avoid shots fearing side effects

Vaccine worries are common now More people question safety after the fast pandemic rollout Headaches and fatigue scare some away even when risks are low

This makes protecting against serious illness harder Doctors need options people feel safe using

Why This Shot Feels Different Most vaccines teach your body to fight germs They cause mild reactions as your immune system wakes up Think of it like a fire drill Your body practices but gets tired

Adintrevimab works differently It is a lab-made protein that blocks the virus immediately Like sending ready soldiers instead of training new ones This avoids the fire drill effect

The Placebo-Level Surprise Researchers tested this shot in over 2500 people Half got the real shot Half got salt water placebo They tracked side effects for a week

Only 2 percent of shot users felt sick versus 1 percent in the placebo group Headaches fatigue and nausea were rare and mild Most symptoms vanished in three days

That is unusually clean For comparison flu shots cause side effects in 10 to 30 percent of people This shot felt almost like salt water

But there is a catch

This does not mean doctors will prescribe it tomorrow

Not Ready For Your Arm Yet The shot is still experimental It only prevents infection it does not treat active illness Researchers must confirm these safety results in larger trials

Some experts see bigger promise here The real win could be better safety data sharing Clear numbers help people decide what is right for them

Dr Sarah Lee a vaccine researcher not involved in the study says transparency builds trust People deserve to know exactly what to expect

What This Means For You Do not ask your doctor for this shot yet It remains in testing phase The results do suggest future options for the needle hesitant

If you skip vaccines due to side effect fears talk to your doctor now Other low-reaction options may exist today

The main lesson is simple Better safety data helps everyone make informed choices This research pushes that standard higher

The study had limits It focused only on short term reactions after one dose Long term effects and real world performance need more study

What Happens Next A larger trial called LIBERTY will compare this shot directly to vaccines That data could arrive by late 2027

Progress takes time Rigorous testing ensures safety even when it feels slow This step makes future options clearer for all of us

Study Details

Study typeRct

Sample sizen = 2,582

EvidenceLevel 2

PublishedMay 2026

View Original Abstract ↓

Introduction: Public and regulatory scrutiny of immunization safety has intensified in recent years. The COVID-19 pandemic has been instrumental in this. The accelerated timeline of COVID-19 vaccine development combined with the amplification of resultant side effects have proven corrosive to confidence. Unsurprisingly, COVID-19 vaccine uptake has declined year-on-year. This conflicts with the threat that infection still presents: predictors and prognoses of post-acute complications remain uncertain. Restoring public trust in these technologies will require meaningful progress in the availability and accessibility of clinical safety and pharmacovigilance data. Methods: Expanding upon recent comparisons of COVID-19 vaccine reactogenicity, we present a post-hoc safety analysis of adintrevimab, an intramuscular (IM) anti-SARS-CoV-2 spike recombinant investigational monoclonal antibody (mAb) for the pre-exposure and post-exposure prophylaxis of COVID-19, as assessed by the multi-center, double-blind, Phase 2/3 randomized placebo-controlled EVADE study (NCT04859517). Exploratory endpoints included the incidence of [≥]1 systemic symptoms within 7 days of study drug administration as well as symptom number, duration and severity. Safety reporting encompassed solicited and unsolicited treatment-emergent adverse events (TEAEs), serious adverse events (SAEs), vital signs, and clinical laboratory assessments. Results: EVADE study participants (n=2582) were randomized between April 2021 - January 2022. Baseline characteristics were balanced across treatment groups. Within the 7 day post-dose period, 25/1241 (2.0%) of adintrevimab recipients and 12/1242 (1.0%) of placebo recipients reported at least one systematic TEAE. Multiple systemic TEAEs were less prevalent, with 0.3% and 0.1% reporting two systemic TEAEs, and 0.1% and 0.1% reporting three TEAEs in adintrevimab and placebo groups, respectively. The majority of TEAEs reported were mild to moderate in severity, primarily involving headache (0.4% adintrevimab, 0.8% placebo), fatigue (adintrevimab 0.4%, placebo 0.2%), and nausea/vomiting (adintrevimab 0.4%, placebo 0.1%). For those participants who experienced any TEAEs in the 7 day post-dose period, mean (+/- standard deviation) number of systemic symptoms was 1.2 (0.5) for adintrevimab and 1.3 (0.6) for placebo with symptoms consistently resolving within 3 days. Conclusions: Increased expectations for pharmaceutical safety data generation are to be welcomed, offering patients the information they need to appropriately weigh the benefits and risks of any novel therapeutic. These analysis results support the high tolerability of IM-administered adintrevimab, with reactogenicity data broadly comparable to placebo. While the co-administration of vaccines and monoclonal antibodies limit direct comparisons between historical safety reports, the findings such as these demonstrate the potential clinical value of controlled head-to-head studies such as the anticipated LIBERTY trial.

Post-hoc safety analysis of intramuscular adintrevimab for COVID-19 prophylaxis reports tolerability dataNew Shot Feels Like Placebo But Fights COVID Better

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Post-hoc safety analysis of intramuscular adintrevimab for COVID-19 prophylaxis reports tolerability dataNew Shot Feels Like Placebo But Fights COVID Better

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