Covid Vaccines: Is the 2nd Dose Different?

[mktsgm]

TL;DR Summary

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.

 

[.Scott]

For the Pfizer vaccine:
FDA Pfizer Fact Sheet (middle of page 3)

The Pfizer-BioNTechCOVID-19 Vaccine is administered intramuscularly as a series of two doses (0.3mL each) 3 weeks apart.

For the Moderna vaccine:
FDA Moderna Fact sheet (towards end of page 3)

Each dose must contain 0.5 mL of vaccine.

For the 2-dose COVID vaccines available in the US, if both doses are properly administered , they will be identical.

 

[jim mcnamara]

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.

 

[mktsgm]

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.