WHO expert on immunization Anne Lindstrand said this on July 12 at a briefing that broadcast on the organization’s YouTube channel.
“As with other vaccines, the effectiveness of the coronavirus vaccine diminishes over time. But research shows that overall vaccines provide a fairly high level of protection,” she said.
At the same briefing, WHO Chief Scientist Sumya Swaminatan added that there is now a tendency in the world when countries with a sufficient number of vaccines are beginning to think about booster doses or mixing different drugs for immunization.
“This is a somewhat dangerous trend. We are in a zone of lack of data and evidence regarding vaccine mixing. The situation in countries will be chaotic if citizens begin to decide when and who will take the second, third and fourth doses,” she said.
An outbreak of coronavirus infection began at the end of 2019 in China. 11 March 2020 WHO declared the spread of coronavirus a pandemic.
The coronavirus vaccination campaign began in late 2020. In April 2021, the World Health Organization stated that the consequences of vaccination against coronavirus drugs of different types are unknown.
In May in the magazine The Lancet preliminary research results from the University of Oxford were published. Volunteers received one vaccine against AstraZeneca and one from Pfizer / BioNTech. According to the results, an increase in adverse reactions was recorded, but none of them were serious or long-term.
Preliminary results of a study by scientists from the Carlos III Institute of Health in Spain, published in May, indicate that the combined use of coronavirus vaccines from Pfizer / BioNTech and Oxford / AstraZeneca provides a powerful immune response.
In July Turkey and Israel allowed to administer a booster dose of the coronavirus vaccine, and according to media reports, the company Pfizer intends to inform US authorities about the need for a booster dose; decided to mix different drugs, in particular, in Thailand and Canada.
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