Striving to improve its COVID-19 vaccination coverage, Turkey is pursuing all options available. After a deal with Russia for Sputnik V, the country announced it has also modified the period between the two doses of Comirnaty, a vaccine developed by Pfizer-BioNTech.

Following a meeting of the Coronavirus Scientific Advisory Board Wednesday evening, Turkey's Health Ministry announced that they discussed a new finding where some people started developing immunity against the coronavirus within 12 days of inoculation. Officials said Uğur Şahin, the Turkish German co-founder of BioNTech, was consulted in relation to this new finding and it was decided to administer the second dose six to eight weeks after the first shot. Previously, this period was four weeks.

The decision will likely help Turkey boost its vaccination drive. The nation of 84 million has delivered the first shot to more than 13.6 million people and the full two doses to nearly 9 million since launching its vaccination drive with China's CoronaVac jab in mid-January.

The country has acquired around 4.5 million doses of the Pfizer-BioNTech vaccine and expects to increase this number to 30 million by June.

Experts say the gap between the two shots is not something to worry about. Murat Akova, a professor at the Faculty of Medicine at Hacettepe University in the capital Ankara, says the decision mainly stemmed from difficulty in obtaining vaccines and pointed out that Britain followed a similar approach with a three-month period between the two shots of the AstraZeneca vaccine.

Health Minister Fahrettin Koca said after the meeting on Wednesday that the next two months will be "difficult" for obtaining vaccines but they expected "an abundance of vaccines" after that, pointing out the increasing number of vaccine producers and their increased production capacity.

Akova told the Sabah newspaper that the Pfizer-BioNTech vaccine is still protective and its first dose had "a higher rate of protection" compared to CoronaVac. "Still, its impact can also be seen after two weeks following the second dose. People who received their first dose should continue taking their own measures against coronavirus infections," he warned.

Derya Unutmaz, a professor at the U.S.-based Jackson Laboratory, a biomedical research institute, said he would also recommend a longer period between the two doses "because there is 70% of protection provided by the vaccine after the first dose," while noting that a second dose, even if it is done two months later, was "absolutely necessary."

BioNTech's vaccine makes up a large share of the doses administered in North America, where it is more commonly known as the Pfizer shot, and the European Union, which is poised to place a massive, multi-year order of 1.8 billion doses in the coming days as the world races against time for inoculation.

Şahin told reporters on Wednesday that data from people who have received the vaccine show that the immune response gets weaker over time, and a third shot will likely be required. Studies show the efficacy of the vaccine declines from 95% to about 91% after six months, he said. "Accordingly, we need a third shot to get the vaccine protection back up to almost 100% again," Şahin told reporters during a video call.

Vaccine recipients currently receive a second dose three weeks after their first shot in most places, although some countries have longer intervals. Şahin suggested the third should be administered nine to 12 months after the first shot. "And then I expect it will probably be necessary to get another booster every year or perhaps every 18 months," he said.

Concerns have been raised that existing vaccines might be less effective against new variants of the virus now emerging in different parts of the world. Şahin said BioNTech has tested its vaccine against more than 30 variants, including the now-dominant one first detected in Britain, and found the shot triggers a good immune response against almost all of them in the lab. In cases where the immune response was weaker, it remained sufficient, he said, without providing exact figures.

Turkey is also working to produce its own vaccine. A state-run platform endorses seven vaccine candidates currently in development. An inactive vaccine completed its Phase II trials and appears to be closest to emergency use approval. An innovative, virus-like particle (VLP) vaccine will likely move up to the Phase II study by the end of May. Other vaccine candidates include an intranasal spray vaccine and an adenovirus-based vaccine similar to Russia’s Sputnik V.