Characteristics of Oral Adverse Effects following COVID-19 Vaccination and Similarities with Oral Symptoms in COVID-19 Patients: Taste and Saliva Secretory Disorders

Abstract

Although coronavirus disease 2019 (COVID-19) vaccines exhibit diverse side effects, taste and saliva secretory disorders have remained poorly understood despite their negative impact on the overall quality of life. The present study aimed to characterize oral adverse effects following COVID-19 vaccination and assess their similarities with oral symptoms in COVID-19 patients. A literature search was conducted in databases, including PubMed, LitCovid, and Google Scholar, to retrieve relevant studies. The narrative review indicated that a certain number of vaccinated people develop ageusia, dysgeusia, hypogeusia, xerostomia, and dry mouth, while they are rare compared with COVID-19 oral symptoms. The prevalence of oral adverse effects varies by country/region and such geographical differences may be related to the type of vaccine used. Similar to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, COVID-19 vaccination adversely affects taste perception and salivary secretion in females and older subjects more frequently than in males and younger subjects. Their impairments mostly appear within 3 days of vaccination, and bitter taste is specifically impaired in some cases. Considering that oral adverse effects following COVID-19 vaccination share some characteristics with oral symptoms in COVID-19 patients, it is speculated that the spike protein derived from COVID-19 vaccination and SARS-CoV-2 infection may be pathophysiologically responsible for taste and saliva secretory disorders. This is because such spike protein has the potential to interact with ACE2 expressed on the relevant cells, produce proinflammatory cytokines, and form antiphospholipid antibodies. Our results do not deny the advantages of COVID-19 vaccination, but attention should be paid to post-vaccination oral effects in addition to COVID-19 oral symptoms. Although coronavirus disease 2019 (COVID-19) vaccines exhibit diverse side effects, taste and saliva secretory disorders have remained poorly understood despite their negative impact on the overall quality of life. The present study aimed to characterize oral adverse effects following COVID-19 vaccination and assess their similarities with oral symptoms in COVID-19 patients. A literature search was conducted in databases, including PubMed, LitCovid, and Google Scholar, to retrieve relevant studies. The narrative review indicated that a certain number of vaccinated people develop ageusia, dysgeusia, hypogeusia, xerostomia, and dry mouth, while they are rare compared with COVID-19 oral symptoms. The prevalence of oral adverse effects varies by country/region and such geographical differences may be related to the type of vaccine used. Similar to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, COVID-19 vaccination adversely affects taste perception and salivary secretion in females and older subjects more frequently than in males and younger subjects. Their impairments mostly appear within 3 days of vaccination, and bitter taste is specifically impaired in some cases. Considering that oral adverse effects following COVID-19 vaccination share some characteristics with oral symptoms in COVID-19 patients, it is speculated that the spike protein derived from COVID-19 vaccination and SARS-CoV-2 infection may be pathophysiologically responsible for taste and saliva secretory disorders. This is because such spike protein has the potential to interact with ACE2 expressed on the relevant cells, produce proinflammatory cytokines, and form antiphospholipid antibodies. Our results do not deny the advantages of COVID-19 vaccination, but attention should be paid to post-vaccination oral effects in addition to COVID-19 oral symptoms.

Keywords: COVID-19; Oral adverse effect; Saliva secretory disorder; Taste disorder; Vaccination.

Fig. 1.

Prevalence of taste disorders and saliva secretory disorders following COVID-19 vaccination.

Fig. 2.

Prevalence of post-vaccination taste and saliva secretory disorders varying by country or region. Ageusia (a), dysgeusia (b), hypogeusia (c), xerostomia (d), and dry mouth (e).

Fig. 3.

Prevalence of post-vaccination taste disorders (a) and saliva secretory disorders (b) compared between different types of COVID-19 vaccines. *p < 0.05 and **p < 0.01 compared with a different type of vaccine. mRNA, mRNA vaccine; Vector, adenoviral vector vaccine; Subunit, spike protein subunit vaccine; Inactivated, inactivated virus vaccine.

Fig. 4.

Usage rates (in percentage) of different types of COVID-19 vaccines in individual countries. World (a), Europe (b), the UK (c), Germany (d), Poland (e), Czech (f), Slovakia (g), the USA (h), Mexico (i), Australia (j), Saudi Arabia (k), Turkey (l), Pakistan (m), India (n), and China (o). mRNA, mRNA vaccine; Vector, adenoviral vector vaccine; Subunit, spike protein subunit vaccine; Inactivated, inactivated virus vaccine.

Fig. 5.

Comparison of prevalence of post-vaccination taste and saliva secretory disorders between different types of COVID-19 vaccines used in Europe, the UK, Germany, and Poland. mRNA, mRNA vaccine; Vector, adenoviral vector vaccine; Subunit, spike protein subunit vaccine; Inactivated, inactivated virus vaccine.

Fig. 6.

Relative prevalence (in percentage) of taste and saliva secretory disorders in female and male COVID-19 vaccine recipients of various countries (a) and in female and male COVID-19 patients of various countries (b).

Fig. 7.

Relative prevalence (in percentage) of taste and saliva secretory disorders in younger and older COVID-19 vaccine recipients of various countries (a) and in younger and older COVID-19 patients of various countries (b).

Fig. 8.

Onset and persistence time of ageusia or dysgeusia following COVID-19 vaccination and in COVID-19 patients.