We cannot rule this out, but it seems very unlikely to me. The more I read about it, the less likely it seems. - Laika was launched aboard Sputnik 2 in October

We cannot rule this out, but it seems very unlikely to me. The more I read about it, the less likely it seems. - Laika was launched aboard Sputnik 2 in October 1957 - Gagarin on Vostok 1 in April 1961 Sputnik 2 was much lighter than the Vostok capsule (500 kg vs. 2,500 kg) and did not feature any re-entry apparatus. In just 3.5 years, the Soviets had to improve their carrier rocket and develop a man-rated capsule with a heat-shield and braking system, a guidance system and had to improve the whole life-support system. We know they launched dogs on the Vostok in Dec. 1960, so it is unlikely they'd launch a cosmonaut in the time before. So the time-span between the end of 1960 and April 1961 seems like the only time they could have lost cosmonauts. That just does not seem that much time and I have a hard time believing they managed to lose two cosmonauts in four months. After the death of Komarov in April 1967, they took 1.5 years to fix their design till the launch of Soyuz 2. Likewise, they needed 2+ years after the Soyuz 11 tragedy to launch again. I don't believe they would have just launched a couple of cosmonauts nilly-willy after a deadly accident.