Inclusion criteria:
Having Iranian citizenship or in the case of foreign nationals with a legal residence permit
Age 18 years and older
History of full vaccination with one of the following vaccines: Sinopharm, Razi Cov Pars, Pastocovac, Spikogen, AstraZeneca, Fakhra, or Barkat at least 5 months before the study
Minimum 5 and maximum 9 months interval between the last vaccine dose and the current study participation
In the last six months, the person has not had a confirmed Covid-19 disease based on laboratory evidence or confirmed by a physician
Signing a written informed consent form
Using at least one reliable contraceptive method (condom, oral contraceptive pills, intrauterine contraceptive device, IUD, Norplant capsule) for women of reproductive age 18 to 49 years until 3 months after receiving the booster dose
Negative pregnancy test (baby check) on the day of vaccination
Exclusion criteria:
History of allergic reactions after receiving any previous Covid-19 vaccines or any other drug or vaccine
Having any acute or chronic illness requiring continuous ongoing medical or surgical care within the last months
History of severe cardiovascular disease such as heart failure, or hospitalization due to heart disease within the last year
Pregnancy declared by the participant based on the first day of the last menstrual period (LMP)
Breastfeeding
History of receiving any vaccine within 14 days of receiving the intranasal booster dose
Received blood and/or any blood products and/or immunoglobulins within three months prior to the intranasal booster dose
Diagnosed (suspected or confirmed) with immunocompromising illneses, history of long-term use of immunosuppressive drugs, including history of long-term use of systemic corticosteroids equivalent to 10 mg or more daily prednisolone for more than 14 consecutive days with the exception of topical steroids within the last 4 months
Recent diagnosis or treatment of cancers except basal cell carcinoma and In-situ cervical cancer
History of uncontrolled serious psychiatric illnesses
History of blood disorders (dyscrasia, coagulopathy, platelet deficiency or disorder, or deficiency of blood clotting factors)
History of chronic neurological diseases (including seizures and epilepsy)
Current substance or alcohol abuse
Acute febrile illness at the time of receiving the booster dose
Splenectomy for any reason
Close contact with a confirmed COVID-19 case within two weeks before participating in the current study
Continued use of anticoagulants such as coumarin and related anticoagulants (such as warfarin) or new oral anticoagulants / antiplatelet agents. Note: Less than 325 mg of aspirin per day as prophylaxis is allowed
Chronic unstable diseases in the last 4 weeks, including hospitalization due to surgery, deterioration of one of the organ system's function, a need to add new drugs or serious dose adjustments for existing drugs