Recently, Jaewjaroenwattana et al. introduced a sensor that combined an innovative disposable paper-based immunosensor with a cost-effective plant-based anti-SARS-CoV-2 monoclonal antibody CR3022, expressed in Nicotiana benthamiana. Cellulose nanocrystals were modified on a screen-printed graphene electrode to provide an abundance of COOH functional groups on the electrode surface, resulting in a high capacity for antibody immobilization. It offered a linear relationship in the range of 0.1 pg/mL to 500 ng/mL and a low limit of detection at 2.0 fg/mL. The reported paper-based immunosensor was extended to quantify the RBD level in spiked saliva samples, demonstrating the wide applicability of this system. Paulose et al. have developed a biosensor based on EDL-gated BioFETs to detect cDNAs and viral RNAs under different testing conditions, such as temperature treatments and matrix insensitivity. The BioFETs exhibit high selectivity between cDNA and ncDNA, and the system successfully detects SARS-CoV-2 N-gene RNA in diluted human saliva with a 95°C and a 25°C treatment. This biosensor has potential for on-site COVID-19 screening, which can benefit the healthcare system by improving disease control. As COVID-19 has been a global hot topic with many reviews avaiable, this review will not dive deep into COVID-19-related biosensors. Nidzworski et al. reported a universal diamond biosensor was developed for the specific and sensitive detection of the influenza virus. The diamond electrode was functionalized with polyclonal anti-M1 antibodies to capture the universal biomarker M1 protein. The absorption of M1 protein onto the electrode altered its electrochemical impedance spectra, allowing for sensitive detection. The biosensor achieved a limit of detection of 1 fg/mL in saliva buffer and was able to detect different strains of influenza A virus. This biosensor has the potential to be a rapid and sensitive tool for the early diagnosis of influenza virus infections. A new magnetic beads-based electrochemical immunoassay for the determination of hypoxiainducible factor-1 alpha (HIF-1α) has been reported by Munoz-San Martin et al. The immunoassay involves a sandwich immunoassay using magnetic immunoconjugates of carboxylic acid-microsized magnetic particles (HOOC-MBs) modified with a specific antibody, which were used to selectively capture the target protein. The detection was carried out using amperometric detection at disposable screen-printed carbon electrodes (SPCEs). The immunoassay showed great analytical performance in terms of selectivity and low limit of detection (76 pg mL-1) for HIF-1α.