On Wednesday, Germany confirmed that Bayern Munich defender Niklas Sule – who is fully vaccinated – had tested positive for COVID-19. He was immediately placed into quarantine.
Squads no longer have to do mandatory PCR testing, but Germany elected to do so. With Sule testing positive, Serge Gnabry, Jamal Musiala, Karim Adeyemi and Joshua Kimmich were classed as close contacts and had to leave the training camp to isolate.
Another four players, who have not been named, were also said to have contact with Sule, but were allowed to remain at the camp. They will train alone and be monitored closely over the coming days.
Apart from Sule, no other positive cases were recorded.
While the vaccination status of Adeyemi, Musiala and Gnabry is not known, Bayern star Kimmich has publicly revealed he wishes to wait for more research to be completed on the vaccines before taking up the offer.
Though he would have preferred to avoid the subject and instead focus on Germany's World Cup qualifiers against Liechtenstein and Armenia, Flick reiterated his opinion that everybody should get vaccinated, but also stressed it must be down to the individual to make such a decision.
"There are enough experts who deal with it," Flick told a news conference on Wednesday.
"They have come to the conclusion that there is no compulsory vaccination. There are people in all areas who do not get vaccinated.
"We are in the public eye. We also have a great responsibility. But I've said everything about how I feel about it.
"I want the players to be vaccinated, but that's up to them. I hope that there will no longer be issues such as the five players we have to send home due to coronavirus, that is what I would like as a coach."
There has been a suggestion that players who are unvaccinated may not be able to compete at the 2022 World Cup.
"Qatar is still a long way off, we will see what comes next," he added.
"Our team doctor said enough yesterday. The fact is that we thought about it beforehand and tested ourselves. We feel it is our responsibility to ensure that we are all healthy.
"That something like this would happen to us was almost foreseeable. But we have no compulsory vaccination. I believe that people should not be judged who do not get vaccinated.
"For me the only way out of the pandemic is to get vaccinated – even in professional football. That is my opinion. But everyone has the right to refuse."
Flick also confirmed that Julian Draxler would miss Thursday's match against Liechtenstein with a muscle injury.