What are the latest medical updates on infectious diseases, including new vaccines and antiviral medications?

Latest Medical Updates on Infectious Diseases: Vaccines and Antiviral Medications

Influenza Vaccination Updates

Annual influenza vaccination is recommended for all individuals 6 months and older using either trivalent or quadrivalent inactivated vaccines, with no preference between formulations. 1

Key Vaccination Recommendations

• Live attenuated influenza vaccine (LAIV4) should not be used in any setting, as evidence demonstrates poor effectiveness against influenza A (H1N1)pdm09 viruses in recent seasons 1

• All children with egg allergy of any severity can receive influenza vaccine without any additional precautions beyond those recommended for routine vaccinations 1

• Healthcare personnel must receive annual influenza vaccination as a crucial step in preventing healthcare-associated influenza infections, particularly because they care for individuals at high risk for complications 1

• Influenza vaccine can be safely administered during antibiotic treatment, as antibiotics do not interfere with the immune response to inactivated influenza vaccines 2

• Vaccination should not be delayed solely because a patient is on antibiotic therapy, provided the patient has no fever and is not severely ill 2

Timing Considerations

• Inactivated influenza vaccines can be administered during antiviral therapy without concern for reduced efficacy 3

• Live attenuated influenza vaccine should not be given until 48 hours after cessation of antiviral therapy, and influenza antivirals should not be administered for 2 weeks after LAIV receipt 1, 3

• Minor illnesses with or without fever do not contraindicate influenza vaccination, so patients can receive the vaccine once recovered from flu symptoms 3

Antiviral Medications for Influenza

Pediatricians should promptly identify children suspected of having influenza for rapid antiviral treatment when indicated, as best results are seen when treatment is initiated within 48 hours of symptom onset. 1

Treatment Recommendations

• Oseltamivir and zanamivir are the recommended antiviral medications based on viral surveillance showing >99% of currently circulating influenza strains are sensitive to these drugs 1

• Amantadine and rimantadine should not be used due to high levels of resistance among circulating influenza A viruses 1

• Antiviral treatment is recommended as soon as possible for patients with confirmed or suspected influenza who have severe, complicated, or progressive illness or require hospitalization 1

• Antiviral treatment is recommended for outpatients at higher risk for influenza complications based on age or underlying medical conditions, with clinical judgment being an important component 1

• Oseltamivir may be used for treatment or chemoprophylaxis of influenza among infants aged <1 year when indicated 1

Chemoprophylaxis Guidelines

• Postexposure chemoprophylaxis should only be used when antivirals can be started within 48 hours of the most recent exposure 1

• Preexposure chemoprophylaxis should be reserved for persons at very high risk (e.g., severely immunosuppressed patients) who cannot otherwise be protected during high-risk exposure periods 1

• Chemoprophylaxis is not a substitute for influenza vaccination and should be used judiciously to avoid promoting antiviral resistance 1

COVID-19 Antiviral Medications

Nirmatrelvir/ritonavir (Paxlovid) represents a major advancement in oral antiviral therapy, reducing disease progression by 89% when given within 5 days of symptom onset. 4

Nirmatrelvir/Ritonavir (Paxlovid) Efficacy

• Treatment with nirmatrelvir/ritonavir in nonhospitalized vaccinated patients was associated with a 45% relative risk reduction in emergency room visits, hospitalization, or death at 30 days 5

• Significant reductions in multisystem symptom burden and complications including lower respiratory tract infection and cardiac arrhythmia were observed in treated patients 5

• Oral antivirals offer treatment in outpatient settings with dissemination available on a larger scale compared to parenteral monoclonal antibodies and remdesivir 4

Critical Timing and Usage Considerations

• Antiviral drugs must be prescribed within 5 days of confirmed COVID-19 diagnosis to be associated with lower risks for mortality and progression to serious conditions in patients >60 years of age 6

• No significant clinical benefit was found if prescribed beyond 5 days of diagnosis 6

• Antiviral drugs are severely underutilized, with reported use among the general adult population being ≤35% despite recommendations for high-risk patients 7

Barriers to Antiviral Use

• Among patients not offered treatment, provider reasons included symptom duration >5 days (22.7%), concern about drug interactions (5.7%), or absence of symptoms (22.7%) 7

• Nearly half of patients not offered treatment had no documented reason other than mild symptoms, with limited follow-up consisting only of telephone calls 7

• Education of patients, providers, and medical personnel combined with advance planning for positive test results is needed to improve antiviral medication use 7

Combined Vaccine and Antiviral Effectiveness

Both oral antiviral drugs and COVID-19 vaccines are associated with lower risks for mortality and progression to severe disease, with their joint effects being additive rather than interactive. 6

• No significant interaction effects were observed between antiviral drugs and vaccinations, meaning their benefits add together without interference 6

• Among patients >80 years of age, 3-4 doses of mRNA vaccine (Comirnaty) were associated with significantly lower risks for severe outcomes 6

• Policies should encourage COVID-19 vaccination and ensure oral antivirals are accessible to infected persons within 5 days of confirmed diagnosis 6

Mechanism of Action

• Nirmatrelvir acts on the viral protease while molnupiravir acts on the viral polymerase, each given for 5 days 4

• Antiviral drugs increase cell resistance to viruses, suppress virus adsorption, or inhibit nucleic acid synthesis through various mechanisms including polymerase inhibition, protease inhibition, and integrase inhibition 8

• Ritonavir is a peptidomimetic inhibitor of HIV-1 protease that renders the enzyme incapable of processing viral polyprotein precursors, leading to non-infectious immature viral particles 9