Respiratory Diseases Roundup

New Data on Long COVID, Vaccine Effectiveness, Kidney Risk, Household Transmission, and Influenza Vaccine Coadministration

Edited by:
Ashton L. Stahl

Key Highlights

  • A 58-hospital cohort identified PASC in 16.28% of COVID-19 cases, more than twice the proportion captured by code-based surveillance.

  • Recent COVID-19 vaccination in primary household cases was associated with reduced SARS-CoV-2 transmission risk.

  • Early VA data found LP.8.1-adapted BNT162b2 vaccine effectiveness of 57% against ED/urgent care COVID-19 visits.

  • COVID-19 was associated with higher risks of AKI, CKD, and ESRD than influenza in a large claims analysis.

Phenotyping Shows Long COVID Burden¹

A retrospective cohort study in JAMA Network Open evaluated postacute sequelae of SARS-CoV-2 infection (PASC) across 58 hospitals and affiliated clinics in 4 US regions. The study included 457,950 adults with laboratory-confirmed SARS-CoV-2 infection or a COVID-19 diagnosis code in electronic health record data collected from 2017 to 2025. Researchers used a custom artificial intelligence algorithm, Precision Phenotyping for Research Cohorts, to estimate PASC prevalence, chronic disease burden, organ system distribution, and temporal trends from 2020 through 2024.

The algorithm identified 74,560 PASC cases, representing 16.28% of all COVID-19 cases. This was more than twice the proportion identified through code-based surveillance, which captured less than 7% of cases. Of patients identified with PASC, 66,587 (89.31%) had at least 1 chronic condition. Systemic symptoms were the most common manifestations across sites, followed by respiratory and gastrointestinal symptoms. The authors also reported that PASC prevalence continued to increase through mid-2024, suggesting an accumulating rather than resolving clinical burden. They concluded that current diagnostic coding captures fewer than one-half of cases and may obscure chronic disease needs that require surveillance infrastructure and integrated care pathways.

Recent Vaccination and Household Spread²

A prospective, case-ascertained household transmission study in JAMA Network Open examined whether recent COVID-19 vaccination was associated with SARS-CoV-2 transmission and infection within households. The study enrolled primary case participants from outpatient settings in New York, Tennessee, and Washington from January 1, 2024, to January 31, 2025. Included households had a first member with confirmed SARS-CoV-2 infection and participating household contacts. Participants provided demographic information, vaccination history was verified by study staff, and participants were instructed to collect daily nasal swabs for 10 days regardless of symptoms.

The analysis included 362 primary case participants and 763 household contacts. SARS-CoV-2 infection was detected in 476 household contacts, corresponding to an overall secondary infection risk of 62.4% (95% CI, 58.7%-65.5%). Household contacts of primary case participants vaccinated 6 months or less before symptom onset had lower infection risk compared with contacts of unvaccinated primary case participants (adjusted relative risk, 0.57; 95% CI, 0.35-0.93). The vaccination status of household contacts was not associated with a statistically significant difference in infection risk. The authors noted that household exposure is a high-contact setting and concluded that recent vaccination may provide indirect benefit by reducing transmission and overall SARS-CoV-2 exposure.

LP.8.1 Vaccine Shows Early Protection³

In Nature Communications, researchers reported early vaccine effectiveness (VE) data for the BNT162b2 LP.8.1-adapted COVID-19 vaccine against emergency department/urgent care and outpatient visits. The study used a test-negative case-control design among adult patients in the US Veterans Affairs Healthcare System who had an acute respiratory infection and underwent SARS-CoV-2 testing between September 10 and November 30, 2025. VE was estimated with multivariable logistic regression adjusted for demographic and clinical characteristics. The journal noted that the article was posted as an unedited early-access manuscript before final editing for publication.

Among 34,455 acute respiratory infection episodes, 10.7% were COVID-19 cases. BNT162b2 LP.8.1 vaccination was documented in 1.2% of cases and 2.6% of controls, with a median time since vaccination of 29 days. Early VE was 57% (95% CI, 39%-70%) against COVID-19 emergency department/urgent care visits and 54% (95% CI, 15%-75%) against outpatient visits. The authors wrote that the findings may inform shared decision-making in clinical practice and support COVID-19 vaccination in populations for whom it is recommended. The data reflect early experience during the 2025-2026 respiratory virus season in a VA population with acute respiratory infection.

Post-COVID Kidney Risk Exceeds Influenza⁴

A large retrospective cohort study in Communications Medicine compared kidney outcomes after COVID-19 with outcomes after influenza and with uninfected controls. Researchers used the Merative MarketScan Commercial Database and records from January 2020 through December 2021. The analysis included 939,241 individuals with COVID-19; 199,071 with influenza but not COVID-19; and 1,878,482 negative controls without COVID-19 or influenza. Outcomes included acute kidney injury (AKI), chronic kidney disease (CKD), end-stage renal disease (ESRD), and glomerular diseases.

During a median follow-up of 324 days, COVID-19 was associated with increased risks of any kidney disease (adjusted hazard ratio [aHR], 1.93; 95% CI, 1.87-2.00), AKI (aHR, 2.74; 95% CI, 2.61-2.87), CKD (aHR, 1.38; 95% CI, 1.32-1.45), ESRD (aHR, 3.22; 95% CI, 2.67-3.88), and glomerular diseases (aHR, 1.28; 95% CI, 1.09-1.50). Influenza was associated with smaller increases in any kidney disease and AKI but not with significant increases in CKD, ESRD, or glomerular diseases. The authors noted that the findings may not generalize to pediatric, elderly, uninsured, Medicare, or Medicaid populations, and that the claims data lacked race and laboratory test results.

Flu Vaccine Coadministration Assessed⁵

A randomized clinical trial in Vaccine evaluated whether simultaneous administration of an inactivated influenza vaccine blunted immunogenicity of an mRNA COVID-19 vaccine. The US multisite trial enrolled persons aged 5 years or older who received either quadrivalent inactivated influenza vaccine or saline placebo at the same time as an initial or booster dose of an mRNA COVID-19 vaccine. Participants assigned to placebo received influenza vaccine 7 to 14 days later. SARS-CoV-2 antibody responses were assessed by pseudovirus neutralization at baseline and 28 days after the mRNA COVID-19 vaccine primary series or booster dose.

Of 335 randomized participants, 157 were assigned to simultaneous vaccination and 150 to sequential vaccination. Postvaccination geometric mean SARS-CoV-2 ID50 titers for the ancestral D614G strain were 4357.1 in the simultaneous group and 4492.3 in the sequential group (P = .79). For the BA.4/BA.5 variant, titers were 1547.8 and 1463.8, respectively (P = .69). The investigators concluded that blunting of mRNA COVID-19 vaccine immunogenicity was not observed with simultaneous administration of influenza vaccine. They also noted that simultaneous vaccination may support timely receipt of recommended vaccines.

References

  1. Tian J, Azhir A, Decaro M, et al. Long COVID persistence and surveillance gaps across 58 US hospitals. JAMA Netw Open. 2026;9(5):e2614909. doi:10.1001/jamanetworkopen.2026.14909

  2. Benist SC, Smith-Jeffcoat SE, Talbot HK, et al. Recent COVID-19 vaccination and risk of SARS-CoV-2 transmission. JAMA Netw Open. 2026;9(5):e2612609. doi:10.1001/jamanetworkopen.2026.12609

  3. Appaneal HJ, Lopes VV, Nguyen JL, et al. BNT162b2 LP.8.1 early vaccine effectiveness against COVID-19 emergency department, urgent care, and outpatient visits. Nat Commun. 2026. doi:10.1038/s41467-026-73798-3

  4. Zhang Y, Ghahramani N, Chinchilli VM, et al. The risk of kidney disease increases following SARS-CoV-2 infection compared to influenza. Commun Med. 2026;6:189. doi:10.1038/s43856-026-01460-6

  5. Walter EB, Schlaudecker EP, Talaat KR, et al. Immunogenicity of mRNA COVID-19 vaccine with either simultaneous or sequentially administered inactivated influenza vaccines: a randomized clinical trial. Vaccine. 2026;72:128072. doi:10.1016/j.vaccine.2025.128072