March 19, 2026

Viral Infection and Cancer

Respiratory Viral Infections Prime Accelerated Lung Cancer Growth
Investigators show that patients previously hospitalized with severe COVID-19 have an increased risk of subsequent lung cancer. Across multiple murine models, severe respiratory viral infections accelerated lung cancer growth, whereas vaccination mitigated infection-enhanced tumor progression. Mechanistically, prior viral pneumonia reprogrammed the lung into a pro-tumor microenvironment marked by the sustained accumulation of tumor-associated neutrophils and heightened immunosuppression. They observed persistent chromatin remodeling at key cytokine loci in immune and structural cells, linking inflammatory memory to tumor-promoting signals. Therapeutically, combined blockade of neutrophil recruitment and programmed death-ligand 1 (PD-L1) restored CD8+ T cell function and suppressed tumor growth. Together, these findings establish a causal link between prior viral pneumonia and lung tumorigenesis, underscoring the need for enhanced surveillance and targeted interventions to reduce post-COVID cancer risk.

COVID: Active Vaccination/Immunity

2024–2025 COVID-19 mRNA Vaccine Effectiveness Against Severe Disease
Investigators used electronic health records from a large South Carolina health system and emulated a target trial comparing adults aged 18 years and older who did and did not receive the 2024–2025 COVID-19 mRNA vaccine. Vaccinated individuals during September 1, 2024–March 15, 2025, were risk-set matched 1:2 to unvaccinated individuals on demographic and clinical covariates using propensity score matching. Primary outcomes were time to COVID-19 ED or more severe care and time to hospitalization through April 16, 2025. The final matched cohort included 30,080 individuals, including 10,029 vaccinated participants. Mean age was 65.5 years, 36.5% male, 66.7% Caucasian; 85.6% had a pre-existing condition. Vaccine effectiveness against ED or more severe care was 41.3% (95% CI, 17.2%–58.4%) and 46.1% (95% CI, 13.6%–66.3%) against hospitalization.

COVID: The Late Phase/PASC/Long COVID

Effectiveness of COVID-19 Vaccination and Prior Infections to Reduce Long COVID Risk During the Pre-Omicron and Omicron Periods
Investigators combined survey information from a cohort of healthcare workers in Quebec, Canada, with immunization registry and laboratory administrative data. They assessed vaccine effectiveness (VE) against COVID-19 and Long COVID, stratified by infection history, using a test-negative design where vaccinated participants were compared to unvaccinated participants during the pre-Omicron period or to those twice vaccinated ≥6 months before laboratory testing during the Omicron period. Analyses included 8,230 COVID-19 participants and 43,361 tested specimens. During the pre-Omicron period, one- and two-dose VE was 75% (95% CI: 64–83) and 95% (95% CI: 84–98) against COVID-19, respectively, and 91% (95% CI: 79–96) and 87% (95% CI: 22–98) against Long COVID, respectively. During the Omicron period, booster dose VE was 41% (95% CI: 34–47) against COVID-19 and 57% (95% CI: 46–66) against Long COVID, waning by six months. Hybrid VE in vaccinated and previously infected individuals ranged from 81% (95% CI: 38–94) to 92% (95% CI: 87–95) regardless of number of doses, prior infecting variant or median time since last immunological event up to nine month

A Randomized Trial of Vitamin D Supplementation and COVID-19 Clinical Outcomes and Long COVID: The Vitamin D for COVID-19 Trial
Investigators conducted a parallel two-group randomized controlled double-blinded trial targeting free-living adults in the United States and Mongolia. Index participants with newly diagnosed COVID-19 were cluster-randomized with up to one of their cohabiting contacts either to an oral vitamin D3 loading dose of 9600 IU/d for two days followed by 3200 IU/day for four weeks or to placebo. The primary outcome was ≥1 healthcare visits (including hospitalization) or death within four weeks among the index participants. Index participants (n = 1747) were 44.9% vitamin D deficient or insufficient (25-hydroxyvitamin D3 <20 ng/mL). Baseline characteristics for the household contacts (n = 277) were similar. The four-week cumulative incidence of healthcare utilization in index participants did not significantly differ between the vitamin D3 (n = 863) and placebo (n = 884) groups [cumulative incidences, 0.28 compared with 0.29; odds ratio (OR), 0.97; 95% confidence interval (CI): 0.75, 1.24]. Impact of vitamin D3 on the prevalence of long COVID at 8 wk (OR, 0.78; 95% CI: 0.59, 1.03). No safety concerns were identified.