My elderly parents 70+ took already 4 dosages of covid vaccine until mid-2022. do they still need to take further dosages to be protected or 4 dosages are enough? are masks more appropriate for them now that cases of covid are increasing?

Future use of either masks or boosters should be a decision by the individual and their doc. In the US fewer than 20% of adults have received the latest boosters and that includes less than 50% of those over 60. The available MRNA vaccines had their most success with the earliest strains. Today the strains are more contagious but also less severe.

We are now in an era when everyone should plan on repeat covid vaccination once a year, as for influenza. The newest vaccines, to cover both previously and currently common strains of the virus, will be available in the next few weeks; your parents should get that vaccine when it is available. Masking is optional, but a good idea in crowds or around friends or family with cough or cold symptoms.