In short: we do not know and therefore it is so important that every single person gets vaccinated.
Herd immunity level depends on both how easy the virus transmits from person to person and on how well the natural or vaccine-induced immunity protects us from infection. With the new virus variants emerging that could spread easier and evade our immunity it is not possible to predict what level of population immunity would be needed to prevent further spread.
COVID-19 vaccines are very effective in preventing severe disease and death, and they reduce but do not eliminate the risk of transmission.
Vaccines are essential to fight this pandemic, however vaccination alone will not stop the pandemic. Everyone should follow simple measures to reduce the virus transmission - keep a physical distance of at least 1 meter from others, wear a well-fitting mask, wash hands frequently and avoid crowded or poorly ventilated places. We will need to continue using all tools at our disposal to protect ourselves and communities from this deadly virus.