Federated learning trains a neural network model using the client's data to maintain the benefits of centralized model training, while maintaining the privacy. However, if the client data are not independently and identically distributed (non-IID) because of different environments, the accuracy of the model may suffer from client drift during training owing to discrepancies in each client's data. This study proposes a personalized federated learning algorithm based on the concept of multitask learning to divide each client model into two layers: a feature extraction layer and a category prediction layer. The feature extraction layer maps the input data to a low-dimensional feature vector space. Furthermore, the parameters of the neural network are aggregated with those of other clients using an adaptive method. The category prediction layer maps low-dimensional feature vectors to the label sample space, with its parameters remaining unaffected by other clients to maintain client uniqueness. The proposed personalized federated learning method produces faster learning model convergence rates and higher accuracy rates for the non-IID datasets in our experiments.

COVID-19 vaccination certificates (CVCs) have played a key role in safe reopening of borders for international travel and trade, so understanding key stakeholder perceptions of enablers and barriers for their effective use is critical. The COVID-19 Vaccination Policy Research and Deci-sion-Support Initiative in Asia (CORESIA) was established to address policy questions related to CVCs. We conducted two online surveys, i.e., one for the public and one for health and non-health sector experts, from June to October 2021 in nine Asian countries. Descriptive analysis identified participants, enablers, and barriers. Most participants (78% public, 89% experts) accepted the use of CVCs, primarily to resume international travel (76%). Most respondents in both surveys wanted the minimum vaccination coverage to be 60% before CVCs were implemented nation-wide. Most of the public (82%) agreed to maintain existing non-pharmaceutical interventions, while most experts wanted risk-based testing and quarantine policy for incoming travellers (51%) and both digital and paper format CVCs (64%). Support for CVCs for international travel remains high in Asia. Recognising key enablers and barriers for effective use of CVCs from COVID-19 pandemic may help policymakers draft effective border policies for future epidemics.