Mexican authorities said Monday that the Russians have been having so many problems producing the second dose of the Sputnik V coronavirus vaccine that Russia probably will be unable to supply enough to people who got the first dose.

It is the latest account of production problems for Sputnik, which the Russian government has been promising to other countries slotxo but has been able to supply in sufficient quantities.

Sputnik is unusual among coronavirus vaccines in that the two doses are different and not interchangeable.

The Russian vaccine uses a modified version of the common cold-causing adenovirus to carry genes for the spike protein in the coronavirus as a way to prime the body to react if COVID-19 comes along.

That is a similar technology to the vaccine developed by AstraZeneca and Oxford University. But unlike AstraZeneca's two-dose vaccine, the Russian approach uses a slightly different adenovirus for the second booster shot.

Mexico's assistant health secretary, Hugo López-Gatell, said the Russians have found that the first adenovirus grows much more quickly than the second.

López-Gatell said Russian scientists are now pushing the idea of ??abandoning the idea of ??giving the two separate compounds several weeks apart and instead giving a second booster shot of the first compound six months apart, an approach called “Sputnik Light.”

"Over the course of months, the quantity of first doses they managed to produce got out of alignment with the quantity of second doses they were able to produce," López-Gatell said.

López-Gatell said there were claims, not yet validated by Mexico's medicines safety agency, that Sputnik Light could be around 80% effective.

Mexico has so far received only 1.9 million Sputnik doses, out of a total of 24 million it signed a contract for. It has been forced to rely more on the Pfizer vaccine, of which it has received 10.6 million doses, as well as about 10 million doses of two Chinese vaccines. It also received about 4.6 million does of AstraZeneca's vaccine.