Usage
- Medical Conditions: Human adenovirus vector vaccines are primarily used for active immunization against infectious diseases. Currently, they are prominently used for protection against COVID-19. Other applications under investigation include vaccines for Ebola, Zika, HIV, human papillomavirus, malaria, respiratory syncytial virus, and MERS.
- Pharmacological Classification: Vaccine (viral vector vaccine).
- Mechanism of Action: These vaccines utilize a modified, replication-deficient adenovirus to deliver genetic material encoding a specific antigen of the target pathogen (e.g., the spike protein of SARS-CoV-2). The adenovirus vector enters cells, and the genetic material is expressed, leading to the production of the target antigen. This triggers an immune response, generating antibodies and cellular immunity against the pathogen.
Alternate Names
- Recombinant adenovirus vector vaccine
- Ad vector vaccine
- Depending on the serotype: Ad5 vector vaccine, Ad26 vector vaccine, ChAdOx1 vector vaccine, AdC68 vector vaccine
Brand Names
- Janssen COVID-19 Vaccine (Ad26.COV2.S), Sputnik V (Gam-COVID-Vac), AstraZeneca COVID-19 Vaccine (Vaxzevria, Covishield), Convidecia (Ad5-nCOV)
How It Works
- Pharmacodynamics: The vaccine elicits both humoral and cellular immune responses. Humoral immunity involves the production of antibodies that neutralize the pathogen. Cellular immunity involves the activation of T cells that can kill infected cells.
- Pharmacokinetics: The adenovirus vector enters cells, but does not replicate. The delivered genetic material is transcribed, and the encoded antigen is produced. The vector and its genetic material are eventually eliminated from the body.
- Mode of Action: The adenovirus vector binds to cell surface receptors (e.g., CAR, CD46) and enters the cell via endocytosis. The viral DNA is released into the nucleus, where the target antigen gene is transcribed and translated. The antigen is then presented on the cell surface, initiating an immune response.
- Elimination Pathways: The adenovirus vector is eliminated through normal cellular processes.
Dosage
Standard Dosage
Adults:
- Janssen (Ad26.COV2.S): Single dose of 0.5 mL intramuscularly.
- Sputnik V (Gam-COVID-Vac): Two doses (0.5 mL each) intramuscularly, 21 days apart (rAd26, then rAd5).
- AstraZeneca/Covishield (ChAdOx1): Two doses (0.5 mL each) intramuscularly, 4-12 weeks apart.
- Convidecia (Ad5-nCOV): Single dose of 0.5 mL intramuscularly.
Children:
- Use in children varies depending on the specific vaccine and regulatory approvals. Consult local guidelines for specific age-based recommendations.
Special Cases:
- Elderly Patients, Patients with Renal/Hepatic Dysfunction, Patients with Comorbid Conditions: Dosage adjustments are typically not required for these populations, but individual patient factors should be considered.
Clinical Use Cases
- Primarily used for pre-exposure prophylaxis of infectious diseases. Specific clinical use cases and recommendations vary depending on the target pathogen and the specific vaccine.
Dosage Adjustments:
- Generally, no dose adjustments are necessary, but individual patient circumstances should be taken into account.
Side Effects
Common Side Effects:
- Injection site pain, redness, swelling
- Fatigue, headache, muscle aches, chills, fever, nausea
- Swollen lymph nodes
Rare but Serious Side Effects:
- Thrombosis with thrombocytopenia syndrome (TTS) (specifically associated with some adenovirus vector vaccines, e.g., Ad26.COV2.S, ChAdOx1)
- Severe allergic reactions (anaphylaxis)
- Guillain-Barré syndrome (rare)
Long-Term Effects:
- Long-term data is still being collected. To date, no long-term adverse effects have been definitively linked to adenovirus vector vaccines.
Contraindications
- Severe allergic reaction (anaphylaxis) to a previous dose of the vaccine or any of its components.
- TTS following a previous dose of an Ad26 or ChAdOx1-vectored vaccine
Drug Interactions
- No clinically significant drug interactions have been identified. However, concomitant administration with other vaccines should be based on local guidelines.
Pregnancy and Breastfeeding
- Data suggest that adenovirus vector COVID-19 vaccines are safe in pregnancy and breastfeeding. Antibodies generated by the mother can be transferred to the fetus or infant, providing passive immunity. However, consultation with a healthcare professional is essential for individual risk-benefit assessment.
Drug Profile Summary
- Mechanism of Action: Delivers genetic material encoding a pathogen antigen, triggering an immune response.
- Side Effects: Common: Injection site reactions, fatigue, headache, muscle aches, fever. Rare: TTS, anaphylaxis, Guillain-Barré Syndrome.
- Contraindications: Severe allergy to vaccine components, history of TTS after an Ad26 or ChAdOx1-vectored vaccine
- Drug Interactions: None clinically significant identified.
- Pregnancy & Breastfeeding: Generally considered safe, but consult with a healthcare professional.
- Dosage: See detailed dosage guidelines above.
- Monitoring Parameters: Monitor for adverse reactions, especially severe allergic reactions or signs of TTS.
Popular Combinations
- Not typically used in combination with other vaccines unless recommended by local guidelines.
Precautions
- Screen for allergies to vaccine components.
- Monitor for signs of adverse reactions.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Human adenovirus vector vaccine?
A: Depends on the specific vaccine. See detailed dosage section above.
Q2: Can adenovirus vector vaccines cause COVID-19?
A: No. They do not contain live SARS-CoV-2 virus and cannot cause COVID-19.
Q3: Are adenovirus vector vaccines safe for immunocompromised individuals?
A: Studies suggest they are generally safe, but further research is ongoing. Consult local guidelines and individual patient factors should be considered.
Q4: What are the common side effects?
A: Injection site reactions, fatigue, headache, muscle aches, and fever.
Q5: What are the rare but serious side effects?
A: TTS (with certain vaccines), anaphylaxis, and Guillain-Barré Syndrome.
Q6: Can pregnant or breastfeeding women receive these vaccines?
A: Generally considered safe, consult a healthcare professional for individual assessment.
Q7: How long does immunity last after vaccination?
A: Duration of immunity is still being investigated. Booster doses may be needed.
Q8: Can different adenovirus vector vaccines be used interchangeably (e.g., Ad26 followed by ChAdOx1)?
A: Consult local guidelines. Some studies suggest this approach may be effective, but standardized recommendations are still evolving.
Q9: How do these vaccines compare to mRNA vaccines?
A: Both are effective. Adenovirus vector vaccines may have easier storage requirements. mRNA vaccines may have a slightly higher efficacy against symptomatic infection in some studies, but both offer substantial protection, especially against severe disease. Head-to-head comparisons are complex and depend on multiple factors.
