It is that time of year when the seasonal flu, known as influenza, affects people across the United States and globally. This highly contagious respiratory illness is caused by three main viral types: Influenza A, B, and C. The infection affects the nose (causing runny nose), throat (leading to sore throat), and lungs (resulting in coughing). Although the flu can begin with symptoms similar to those of a cold, it typically progresses more quickly and is more severe. Other common flu symptoms include:
Influenza A is typically more severe and is currently circulating. A recent article in the Journal of the American Medical Association reviewed the current state of the circulating influenza strain known as Influenza A (H3N2) subclade K virus. They noted that since December 11, 2025, influenza activity has been accelerating in the United States, especially among children and young adults. As would be expected, the primary recommendation for protection against seasonal influenza is vaccination. According to United Kingdom hospital and emergency admission data, the vaccines were 72%–75% effective in children (most of whom received the live-attenuated intranasal vaccine), whereas the injected vaccines for adults were only 32%–39% effective. It is too soon to know how effective the flu vaccine will be this year for the U.S. population. The current vaccine is trivalent, meaning it protects against two influenza A subtypes and one influenza B strain.
One concern regarding influenza vaccines is the presence of thimerosal. This additive, found in some injectable flu vaccines, contains a mercury compound that inhibits the growth of bacteria and fungi. It has been removed from children’s vaccines since 2001, except in some injectable influenza vaccines. The Centers for Disease Control (CDC) maintains that thimerosal is safe. To avoid thimerosal in injectable flu vaccines, individuals can choose thimerosal-free single-dose vials rather than multi-dose vials.
Interestingly, the CDC recommends for the 2025–2026 flu season the following:
“Children aged ≤18 years, pregnant women, and all adults should receive seasonal influenza vaccines only in single-dose formulations that are free of thimerosal as a preservative.”
If thimerosal is safe, why does the CDC recommend this year that people receive injections free of thimerosal? One possible explanation is that the current CDC administration may have concerns about thimerosal and is gathering additional data before any potential change in prior CDC positions. Another option for individuals ages 2 to 49 is a nasal influenza vaccine, such as FluMist, which does not contain thimerosal.
Flu vaccines and antiviral medications are options to discuss with your healthcare provider. Whether or not you choose to use these approaches, the following are protocols I commonly use with patients during the influenza season.
Immune Wellness contains herbal extracts used for long-term immune support, including Turkey Tail, Maitake, and Astragalus. The typical dose is three to four capsules daily.
N-acetylcysteine (NAC) is an antioxidant that also supports immune function. A study found that only 25% of older adults who were injected with the influenza virus experienced influenza symptoms after taking NAC for six months, compared with 79% who received a placebo. A preventative dose is 600 mg twice daily on an empty stomach. In addition, a recent paper published in the journal Antioxidants states:
“NAC can help alleviate the symptoms of influenza, primarily by addressing different mechanisms associated with the infection.”
Vitamin D research indicates that vitamin D reduces the risk of acute respiratory tract infections, including influenza and the common cold. This nutrient acts like a hormone in the body by increasing antiviral white blood cells, controlling inflammation, and elevating levels of two antimicrobial compounds, cathelicidins and defensins. Most of my adult patients take vitamin D3 (5,000 IU) with K2, one capsule daily with meals.
Elderberry is one of the few natural therapies studied in individuals with influenza. A randomized, double-blind, placebo-controlled trial involving sixty Norwegian men and women between 18 and 54 years of age found that 15 mL of standardized elderberry syrup four times daily for five days, when started within 48 hours of influenza-like symptoms, relieved symptoms an average of four days earlier than placebo. None of the participants reported adverse events during the study. Elderberry also helps relieve coughing associated with the flu. This product is available online or in health food stores under the Sambucol brand. Use as directed.
Intravenous therapy, including intravenous nutrients such as vitamin C, may be beneficial for acute influenza symptoms. This approach may provide antiviral effects and hydration for patients prone to dehydration due to influenza-related symptoms and reduced appetite.
References
De Flora S, Grassi C, Carati L, “Attenuation of influenza-like symptomatology and improvement of cell-mediated immunity with long-term N-acetylcysteine treatment,” Eur Respir J. 1997 Jul;10(7):1535-418
Grohskopf, L. A., Blanton, L. H., Ferdinands, J. M., Reed, C., Dugan, V. G., & Daskalakis, D. C. (2025). Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2025–26 Influenza Season. MMWR Morbidity and Mortality Weekly Report, 74(32), 500–507. https://doi.org/10.15585/mmwr.mm7432a2
Martineau, Adrian R, David A Jolliffe, Richard L Hooper, Lauren Greenberg, John F Aloia, Peter Bergman, and Gal Dubnov-Raz et al. “Vitamin D Supplementation To Prevent Acute Respiratory Tract Infections: Systematic Review And Meta-Analysis Of Individual Participant Data”. BMJ,2017, i6583. doi:10.1136/bmj.i6583.9
Thimerosal and vaccines. (2025, October 28). Vaccine Safety. https://www.cdc.gov/vaccine-safety/about/thimerosal.html
Tieu, S., Charchoglyan, A., Paulsen, L., Wagter-Lesperance, L. C., Shandilya, U. K., Bridle, B. W., Mallard, B. A., & Karrow, N. A. (2023). N-Acetylcysteine and Its Immunomodulatory Properties in Humans and Domesticated Animals. Antioxidants (Basel, Switzerland), 12(10), 1867. https://doi.org/10.3390/antiox12101867
Zakay-Rones, Z, E Thom, T Wollan, and J Wadstein. “Randomized Study of The Efficacy And Safety Of Oral Elderberry Extract In The Treatment of Influenza A And B Virus Infections”. Journal Of International Medical Research 32, no. 2 (2004): 132-140. doi:10.1177/147323000403200205.
Zambon M, Hayden FG. Influenza A(H3N2) Subclade K Virus: Threat and Response. JAMA. Published online December 18, 2025. doi:10.1001/jama.2025.25903
