they definitely recommend against it but also stated that if the original company you used isn’t available and the only option is using the other than do it. They don’t recommend getting the second shot outside of the window either but also stated that is that’s the only option give it anyway.
So while they aren’t recommending it they are allowing it
I have heard the second part, but not the first. I think what they’re saying is that if you get a different vaccine, you have to restart the series. The same might go for getting a second dose too far from the first dose.
Here are the CDC interim recommendations: “However, second doses administered within a grace period of 4 days earlier than the recommended date for the second dose are still considered valid. If it is not feasible to adhere to the recommended interval and a delay in vaccination is unavoidable, the second dose of Pfizer-BioNTech and Moderna COVID-19 vaccines may be administered up to 6 weeks (42 days) after the first dose. Currently, only limited data are available on efficacy of mRNA COVID-19 vaccines administered beyond this window.”
Interchangeability:
“Any currently authorized COVID-19 vaccine can be used when indicated; ACIP does not state a product preference. However, COVID-19 vaccines are not interchangeable.
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In exceptional situations in which the vaccine product given for the first dose cannot be determined or is no longer available, any available mRNA COVID-19 vaccine may be administered at a minimum interval of 28 days between doses to complete the mRNA COVID-19 vaccination series. In situations where the same mRNA vaccine product is temporarily unavailable, it is preferable to delay the 2nd dose (up to 6 weeks) to receive the same product than to receive a mixed series using a different product. If two doses of different mRNA COVID-19 vaccine products are administered in these situations (or inadvertently), no additional doses of either product are recommended at this time.
The safety and efficacy of Janssen COVID-19 vaccine administered after an mRNA COVID-19 vaccine has not been established. However, in limited, exceptional situations where a patient received the first dose of an mRNA COVID-19 vaccine but is unable to complete the series with either the same or different mRNA COVID-19 vaccine (e.g., due to contraindication), a single dose of Janssen COVID-19 vaccine may be considered at a minimum interval of 28 days from the mRNA COVID-19 vaccine dose.”
Sounds like if you can’t get a second dose of a mRNA vaccine, then you can get a one-dose vaccine, but it’s not considered part of the series for the first vaccine.