Pandemic & Infectious Disease — 2026-03-22

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Active Outbreak Tracker

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Measles — United States & Global

• Status: Active and under weekly surveillance; CDC updating case counts
• Key Development: The CDC updated its U.S. measles case tracker this week, continuing its weekly reporting cadence. Globally, the CDC's Global Measles Vaccination page — updated within the past six days — tracks the top 10 countries with active outbreaks, reflecting ongoing international spread driven by vaccination gaps.
• Response: CDC continues monitoring and updating its global measles vaccination data, urging clinicians and travelers to ensure MMR vaccine coverage is current.

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Mpox (Clade I & Clade II) — United States & Worldwide

• Status: Outbreaks of both clade I and clade II mpox are occurring in multiple countries; situation summary updated approximately one week ago
• Key Development: The CDC's mpox situation summary confirms that clade I and clade II outbreaks are ongoing globally. Clade I, associated with higher severity, continues to be a particular concern in affected regions.
• Response: CDC maintains active monitoring through its situation summary page and provides guidance for healthcare providers and travelers.

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Respiratory Viruses (COVID-19, Flu, RSV) — United States

• Status: Illness severity data updated as of March 20, 2026; respiratory virus activity levels under ongoing CDC surveillance
• Key Development: CDC's respiratory virus data channel, updated within the past two days, notes that the agency does not anticipate producing additional outlook updates during the remainder of the 2025–2026 respiratory season — a signal that activity is declining toward seasonal baseline. Rt estimates for COVID-19, influenza, and RSV are being tracked across U.S. states.
• Response: CDC's Center for Forecasting and Outbreak Analytics (CFA) continues to publish Rt estimates and illness severity indicators updated as recently as March 20, 2026.

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Vaccine & Treatment Pipeline

• VYD2311 monoclonal antibody (Invivyd): The FDA has agreed to the design of a phase 3 trial evaluating the safety and immunogenicity of VYD2311 — a monoclonal antibody — compared to mRNA COVID-19 vaccines, as well as in co-administration settings. This alignment marks a key regulatory milestone for a potential non-mRNA alternative for COVID-19 protection.

• VAX-31 pneumococcal conjugate vaccine (Vaxcyte): Positive phase 1/2 adult data for VAX-31, a 31-valent pneumococcal conjugate vaccine (PCV) candidate, were published in The Lancet Infectious Diseases on March 19, 2026. Based on results from adults aged 50 and older, Vaxcyte has advanced VAX-31 High Dose into a comprehensive phase 3 adult program. Topline data from the OPUS-1 pivotal noninferiority trial are expected in Q4 2026.

• 2026 Infectious Disease Trial Landscape (Multiple developers): A summary published March 21, 2026 by Contagion Live outlines key therapeutics and vaccines reporting phase 3 data, initiating trials, or filing for regulatory approval this year — covering a broad range of infectious disease indications to watch through the remainder of 2026.

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Expert Analysis

Global health experts are increasingly flagging the compounding effects of conflict and disease as a defining challenge for 2026. According to a MedIndia analysis published March 21, 2026, the intersection of armed conflict and infectious disease outbreaks is among the top global health risks of the year. Conflict zones disrupt vaccination campaigns, damage healthcare infrastructure, and create population displacement — all of which accelerate outbreak dynamics. Experts cited in the analysis warn that this pattern is not new but is intensifying in scope.

Antibiotic resistance is receiving renewed attention as a slow-moving but potentially catastrophic public health threat. Commentary published March 20, 2026 warns that antimicrobial resistance (AMR) represents the "next global health crisis" — one that has been forecast for decades but remains inadequately addressed. The piece underscores that routine medical procedures and infections that are currently treatable could become life-threatening if resistance continues to grow unchecked. Public health commentators have urged that AMR be treated with the same urgency as acute outbreak response.

On the surveillance front, efforts to expand early warning infrastructure are gaining momentum. Colorado's move to join the WHO's Global Outbreak Alert and Response Network (GOARN) reflects a growing recognition among subnational health authorities that infectious disease monitoring requires coordinated global intelligence. While this development was reported in early March 2026 — just outside the strict 7-day window — it exemplifies a broader trend of jurisdictions seeking integration into international outbreak detection systems.

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Global Health Security

FDA Policy and Vaccine Reform Uncertainty: Throughout early 2026, biopharma companies have been navigating sweeping changes at the FDA, including questions around the politicization of the agency. According to BioSpace's 2026 FDA Policy Tracker, concerns have surfaced about regulatory consistency for vaccines and novel therapeutics — including priority review voucher programs and guidelines for personalized therapies. These dynamics are shaping how manufacturers plan clinical development and seek approvals.

CDC Respiratory Season Wind-Down: The CDC has signaled it does not plan to issue additional respiratory illness outlook updates for the remainder of the 2025–2026 season — a policy posture that implies current surveillance infrastructure will continue passively monitoring without active outbreak escalation. This reflects a level of institutional confidence that the season's peak has passed, though baseline surveillance remains active.

IDSA Vaccine Guidelines for Immunocompromised Patients: The Infectious Diseases Society of America (IDSA) published updated 2025 guidelines on the use of COVID-19, influenza, and RSV vaccines in immunocompromised patients, released via Clinical Infectious Diseases in late February/early March 2026. The guidelines address significant risks that respiratory viruses pose to this vulnerable population and provide updated recommendations amid evolving vaccine formulations.

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What to Watch Next

• Vaxcyte OPUS-1 trial readout (Q4 2026): Topline data from the pivotal noninferiority trial for VAX-31, a 31-valent pneumococcal conjugate vaccine, are expected by end of year. If positive, this could represent a significant advance over existing pneumococcal vaccines — particularly for adults aged 50 and older who face higher pneumonia risk.

• Invivyd VYD2311 Phase 3 trial progression: Now that the FDA has agreed to the trial design for this COVID-19 monoclonal antibody, enrollment and early safety data will be closely tracked. A successful trial could offer a viable COVID-19 protection option for individuals who cannot receive or do not respond optimally to mRNA vaccines.

• Measles outbreak trajectories in vaccination-gap regions: With CDC tracking global measles outbreaks weekly and the top 10 affected countries under active monitoring, the trajectory of outbreaks in regions with below-target MMR coverage will be a key indicator of whether the global measles resurgence trend continues or stabilizes through mid-2026.