• An earlier study by Oxford University on mixing Pfizer and AZ vaccines had shown that receiving the two different vaccines as first and second dose induced higher antibodies.
• Kenya is among countries that have been hit by vaccine shortage after the Indian government halted vaccine exports due to satisfy domestic demand.
The World Health Organization has warned against mixing of Covid-19 vaccines, saying there is no scientific evidence to support the same.
The global health agency said the final decision on mixing and matching of vaccines should be left to health experts, as the safety and efficacy of a 'mixed-dose' hasn't been established.
Some countries have decided to give different second doses in the wake of vaccine shortages and supply chain challenges, especially for AstraZeneca.
“It is a little bit of a dangerous trend here. It will be a chaotic situation in countries if citizens start deciding when and who will be taking a second, a third and a fourth dose,” WHO chief scientist Soumya Swaminathan said.
"Data from mix and match studies of different vaccines are awaited - immunogenicity and safety both need to be evaluated," she added.
Kenya is among the countries that have been hit by vaccine shortage after the Indian government halted exports due to rising domestic demand.
The Health ministry is yet to decide whether mixing of vaccines from different manufacturers will be the next viable option.
“In some countries like Spain and Germany, those who received their first dose of Pfizer vaccine or Astrazeneca have gotten the reverse,” acting Health director general Dr Patrick Amoth said.
“Data will emerge from that particular platform to be able to advise us and that is why it is important for us to get other vaccines so that we can try on those in our own local setting,” he added.
The government expects 1.7 million doses of Pfizer vaccine from the US.
Pfizer and Johnson and Johnson vaccines are to be administered to Kenyans who are yet to receive a single shot.
An earlier study by Oxford University on mixing Pfizer and AZ vaccines had shown that receiving the two different vaccines as first and second dose induced higher antibodies.
A similar study by Saarland University in Germany showed a stronger immune response in patients who received Astrazeneca jab followed by Pfizer than in patients who received two doses of Astrazeneca.
The two studies are yet to go through the peer review process, where independent scientists will evaluate them before making the final decision.
Data from the ministry shows that by Saturday, 1,618,356 vaccines had been administered across the country, with 581,003 people having received their second dose.
This means the proportion of the adult population fully vaccinated is 2.1 per cent.
Another 1,037,353 have received their first dose, with the uptake of the second dose among those who received their first dose being at 56 per cent.
In terms of uptake of vaccines per priority groups, 106,100 are healthcare workers, 81,578 are teachers, 46,214 are security officers, 181,225 are people aged 58 years and above, while 165,874 are members of the public.