The national Covid-19 vaccination commission has announced a revised timetable for the period between the first and second doses of both the Sinopharm and Sinovac vaccines, increasing it from 14 to at least 21 days.
The decision was made because studies had shown that the vaccines provided a stronger immune response and better overall protection longer interval, according to the Ministry of Health.
Ministry spokeswoman Or Vandine issued the new directive to all provincial vaccination sub-commissions with orders for immediate implementation.
“Earlier this year the transmission of Covid-19 was so rapid that we felt we should carry out our vaccination campaigns with urgency and haste. Scientists have said that in emergency situations, such as the situation we had in our former red zones or in any places with a rate of transmission, vaccinations can be sped up so that those affected have at least partial protection,” she said.
Vandine said the 14-day interval used until now was due to it being a crisis situation and the two vaccine makers also recommended an interval of between 14 and 21 days. However, some independent studies done in countries other than China have indicated that a period of 28 days is optimal.
“I want our people to understand this matter clearly: Those who had a 14-day interval for vaccinations are not at a significant disadvantage as compared to those who have had an interval of 21 days. Both offer strong protection. But scientists have said that if we wait for one more week, our immune system will produce more antibodies,” she said.
According to Vandine, moving the interval to 21 days was also partly in response to the new Delta variant, and a stronger antibody response could help reduce the overall rate of transmission, hospitalisation and death.
According to the health ministry, all provinces will kick off their vaccination campaigns by July 15. Phnom Penh completed its vaccination campaign on July 8.
In international developments, in response to a reporter’s question about mixed vaccines regimens at a press conference on July 13, Dr Soumya Swaminathan of the World Health Organisation (WHO) said she was not in favour of vaccinating people using different vaccines for the first and second doses. She said doing so may pose a significant – but as yet unknown – risk to people’s health.
Regarding this topic, Vandine said there were no definitive studies completed as yet to determine the efficacy of a mixed regimen of two or more vaccines together and for the time being the ministry did not recommend using different vaccines on one person.
Vandine noted that the Sinovac and Sinopharm vaccines were similar in that they were produced through the same manufacturing methods traditionally used in vaccine development and which was successfully utilised to create the vaccines against diseases like measles and whooping cough.
Some of the other vaccines such as those produced by Pfizer and Moderna were produced through a new method where the RNA – ribonucleic acid – is taken from the virus or a protein of the virus and that is used to induce an immune response rather than simply using inactivated virus cells, she said.
“If the vaccines are produced with different methods and we use different vaccines on one person, will it produce any reaction? Some countries have announced that they will use mixed vaccines, but it is a decision that must be made by their government leaders. Maybe they are doing some kind of trial study? Because there is no clarity on this matter and all countries are very concerned about the Delta variant,” she said.
Vandine called on the public to remain calm and reiterated that there was no need for Cambodia to experiment with mixed vaccines because the Kingdom has sufficient supplies to avoid taking that risk.
She also noted that while the WHO currently recommends taking two doses of vaccines, the option to take a third dose of the same vaccines as a “booster shot” is currently under study.
As of July 13, more than five million out of the 10 million adults in Cambodia’s target population for vaccination have now received their jabs.
The Kingdom projects that it will reach the 10 million person mark in November, whereupon it will consider offering third shots to certain people as well as vaccinating children.