Usage
- Medical Conditions: ChAdOx1 nCoV-19 vaccine is prescribed for active immunization against coronavirus disease 2019 (COVID-19) in individuals 18 years of age and older.
- Pharmacological Classification: Vaccine (viral vector).
- Mechanism of Action: This vaccine utilizes a replication-deficient chimpanzee adenovirus vector to deliver the genetic code for the SARS-CoV-2 spike (S) glycoprotein. This vector enters human cells and prompts them to produce the S protein. The immune system recognizes this protein as foreign, triggering both humoral (antibody) and cellular immune responses that protect against future SARS-CoV-2 infections.
Alternate Names
- Alternate Names/International Variations: AZD1222, ChAdOx1-S [recombinant]
- Brand Names: COVISHIELD™, Vaxzevria, COVID-19 Vaccine AstraZeneca
How It Works
- Pharmacodynamics: The vaccine stimulates the body’s immune system to generate antibodies and cellular immune responses specific to the SARS-CoV-2 spike protein, thereby preventing viral entry into cells and subsequent infection.
- Pharmacokinetics: Administered intramuscularly, the adenovirus vector enters cells at the injection site. The vector itself does not replicate, and the expressed spike protein is presented to the immune system. Elimination pathways are not relevant in the traditional sense for vaccines, as the objective is to trigger an immune response, not to clear a drug from circulation.
- Mode of Action: The adenovirus vector acts as a delivery vehicle, introducing the SARS-CoV-2 S glycoprotein gene into human cells. These cells then produce the S protein, which is displayed on the cell surface, stimulating an immune response.
- Receptor Binding/Enzyme Inhibition/Neurotransmitter Modulation: The adenovirus vector likely binds to cell surface receptors to gain entry into cells. However, the primary mechanism of action is not related to enzyme inhibition or neurotransmitter modulation. The S protein itself binds to the ACE2 receptor on human cells, and the generated antibodies prevent this binding, thereby blocking viral entry.
Dosage
Standard Dosage
Adults:
- 0.5 ml intramuscularly, administered as two separate doses.
- The second dose should be given 4 to 12 weeks after the first. Studies suggest that a longer interval between doses (up to 16 weeks) may enhance efficacy, particularly in settings with vaccine supply constraints or high COVID-19 incidence.
Children (6-17 years):
- Clinical trials are underway to determine the safety and efficacy in children. Dosage recommendations for this age group will depend on the results of these studies. As of February 16, 2025, there is no approved dosage for children under 18.
Special Cases:
- Elderly Patients: No dose adjustment is required for individuals aged 65 and above. Studies have demonstrated a robust immune response in this population.
- Patients with Renal Impairment: Specific dosage adjustments based on renal function have not been explicitly defined. Clinical judgment is necessary.
- Patients with Hepatic Dysfunction: No specific dosage modifications for hepatic impairment have been established. Clinical judgment is recommended.
- Patients with Comorbid Conditions: Dosage modification is generally not required for patients with comorbid conditions like diabetes or cardiovascular disease. However, individualized assessment is important, especially for immunocompromised individuals.
Clinical Use Cases
ChAdOx1 nCoV-19 is intended for general population vaccination to prevent COVID-19. It does not have specific dosing recommendations for clinical settings like intubation, surgical procedures, mechanical ventilation, or ICU use. The standard dosing guidelines apply.
Dosage Adjustments
Dose adjustments are based primarily on age (adults vs. children - awaiting trial results) and may also be influenced by epidemiological factors (e.g., extending the inter-dose interval in situations of high transmission and limited vaccine supply). No adjustments are specified for renal or hepatic dysfunction, but clinical judgment is warranted.
Side Effects
Common Side Effects:
- Injection site pain, tenderness, redness, itching, swelling, warmth, or bruising
- Fatigue
- Headache
- Muscle aches (myalgia)
- Joint pain (arthralgia)
- Fever/Chills
- Nausea
Rare but Serious Side Effects:
- Severe allergic reactions (anaphylaxis)
- Thrombosis with thrombocytopenia syndrome (TTS) (very rare)
- Guillain-Barré syndrome (GBS) (very rare)
Long-Term Effects:
Long-term effects are still under investigation. Currently, data suggest that protection against severe COVID-19 is durable, but further research is necessary to determine the longevity of immunity and the potential for long-term side effects.
Adverse Drug Reactions (ADR):
Clinically significant ADRs primarily involve allergic reactions (anaphylaxis) and TTS. These require immediate medical intervention.
Contraindications
- Absolute: History of severe allergic reaction (anaphylaxis) to any component of the vaccine. Individuals who experienced TTS following a previous dose of any COVID-19 vaccine should not receive ChAdOx1 nCoV-19.
- Relative: Individuals with a current fever should postpone vaccination until they have recovered.
Drug Interactions
- No specific drug interactions have been identified. Co-administration with other vaccines is generally safe.
Pregnancy and Breastfeeding
- Pregnancy: Can be considered if the benefits outweigh the risks. Limited data are available, but current studies have not shown negative impacts on fertility or pregnancy outcomes.
- Breastfeeding: Vaccination is not contraindicated during breastfeeding. Antibodies are excreted in breast milk, which may provide passive immunity to the infant.
Drug Profile Summary
- Mechanism of Action: Recombinant adenovirus vector delivers the SARS-CoV-2 S protein gene, inducing an immune response.
- Side Effects: Common: injection site reactions, fatigue, headache, myalgia, arthralgia, fever/chills, nausea. Rare: anaphylaxis, TTS, GBS.
- Contraindications: History of anaphylaxis to vaccine components, TTS after any COVID-19 vaccine.
- Drug Interactions: No specific interactions identified.
- Pregnancy & Breastfeeding: Can be considered if benefits outweigh risks; compatible with breastfeeding.
- Dosage: 0.5 ml IM, two doses, 4-12 weeks apart (up to 16 weeks in specific situations). No dose adjustment in elderly. Pediatric use not yet approved.
- Monitoring Parameters: Monitor for immediate allergic reactions post-vaccination.
Popular Combinations
Not applicable for vaccines.
Precautions
- Pre-screening for allergies is crucial.
- Pregnancy: Assess individual risks and benefits.
- Breastfeeding: No contraindication.
- Children and Elderly: No dose adjustment in elderly. Pediatric use is under investigation.
- Menstruating Individuals: No specific precautions.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for ChAdOx1 nCoV-19 Corona Virus Vaccine?
A: 0.5 ml IM, two doses, 4-12 weeks apart (up to 16 weeks in some situations). Pediatric use is not yet approved.
Q2: Can pregnant women receive this vaccine?
A: Yes, it can be considered if benefits outweigh potential risks. Current evidence suggests no adverse effects on fertility or pregnancy outcomes.
Q3: What are the most common side effects?
A: Injection site reactions, fatigue, headache, muscle aches, joint pain, and fever.
Q4: Are there any serious side effects?
A: Rarely, severe allergic reactions (anaphylaxis), TTS, and GBS may occur.
Q5: Can I get other vaccines at the same time as ChAdOx1 nCoV-19?
A: Co-administration with other vaccines is generally considered safe.
Q6: How long does the vaccine protection last?
A: The duration of protection is still being studied. Current data suggest good protection against severe disease, but booster doses may be required.
Q7: Does the vaccine prevent all COVID-19 infections?
A: While highly effective, no vaccine offers 100% protection. Breakthrough infections can occur, but they are usually milder than in unvaccinated individuals.
Q8: What should I do if I experience a side effect?
A: Most side effects are mild and self-limiting. Consult a healthcare professional if you have any concerns or if side effects are severe or persistent.
Q9: Is the vaccine safe for immunocompromised individuals?
A: Immunocompromised individuals may have a reduced immune response to the vaccine. Individualized assessment and additional precautions may be necessary.
Q10: Are there any contraindications to receiving this vaccine?
A: Yes, a history of severe allergic reaction to any vaccine component or TTS following any COVID-19 vaccine are contraindications.
