COVID Covid Vaccines: Is the 2nd Dose Different?

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The discussion centers on the composition and dosage of the second dose of COVID-19 vaccines compared to the first. For the Pfizer-BioNTech vaccine, both doses are identical at 0.3 mL each, administered three weeks apart. The Moderna vaccine also has consistent dosing, with each dose containing 0.5 mL. In the case of two-dose adenovirus vector vaccines, such as Sputnik V, the first and second doses differ; the first uses the Ad26 vector and the second uses Ad5 to prevent interference from antibodies developed after the first dose. Conversely, the AstraZeneca vaccine and its counterpart Covishield use the same adenovirus vector, ChAdOx1, for both doses. This differentiation in vaccine design is crucial for effective immune response.
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Is the contents of the second dose, the same as the first dose of covid vaccine?
Many of the Covid vaccines at present need two doses.

Is the second dose, the same as the first dose, in terms of its contents and dosage?

I specifically want to know if there is any variation in the contents of the second dose.

Thanks.
 
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I can see why you asked. It does not seem to be explicitly stated in non-technical documentation.

COVID-19 adenovirus vector 2 dose vaccines:
The Sputnik V vaccine, produced in Russia, uses both Ad26 (dose 1) and Ad5 (dose 2) vector adenoviruses. So what the patient gets in each shot is slightly different.

The AstraZeneca vaccine and an identical one being made in India, called Covishield, use a chimpanzee adenovirus, called ChAdOx1. The first and second dose use identical adenoviruses - AFAICT.

The reasoning for two vector virus types of vaccine is that the patient develops antibodies to the first adenovirus, so the second dose needs to avoid being interfered with by those new antibodies.
 
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jim mcnamara said:
I can see why you asked. It does not seem to be explicitly stated in non-technical documentation.

COVID-19 adenovirus vector 2 dose vaccines:
The Sputnik V vaccine, produced in Russia, uses both Ad26 (dose 1) and Ad5 (dose 2) vector adenoviruses. So what the patient gets in each shot is slightly different.

The AstraZeneca vaccine and an identical one being made in India, called Covishield, use a chimpanzee adenovirus, called ChAdOx1. The first and second dose use identical adenoviruses - AFAICT.

The reasoning for two vector virus types of vaccine is that the patient develops antibodies to the first adenovirus, so the second dose needs to avoid being interfered with by those new antibodies.
Thanks Jim.
 
https://www.discovermagazine.com/the-deadliest-spider-in-the-world-ends-lives-in-hours-but-its-venom-may-inspire-medical-miracles-48107 https://en.wikipedia.org/wiki/Versutoxin#Mechanism_behind_Neurotoxic_Properties https://www.sciencedirect.com/science/article/abs/pii/S0028390817301557 (subscription or purchase requred) he structure of versutoxin (δ-atracotoxin-Hv1) provides insights into the binding of site 3 neurotoxins to the voltage-gated sodium channel...
Popular article referring to the BA.2 variant: Popular article: (many words, little data) https://www.cnn.com/2022/02/17/health/ba-2-covid-severity/index.html Preprint article referring to the BA.2 variant: Preprint article: (At 52 pages, too many words!) https://www.biorxiv.org/content/10.1101/2022.02.14.480335v1.full.pdf [edited 1hr. after posting: Added preprint Abstract] Cheers, Tom
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