inclusion criteria: * able to provide written informed consent * males or females 18 years of age or older * have previously had a primary course of covid-19 vaccine with the most recent dose no less than 3 months previously. * understand and are likely to comply with planned study procedures and be available for all study visits. exclusion criteria * allergy to spikogen vaccine or one of its components, e.g. polysorbate 80. * have received an experimental agent within 30 days prior to the study vaccination or expect to receive another experimental agent during the trial reporting period. * any serious medical, social or mental condition which, in the opinion of the investigator, would be detrimental to the subjects or the study.

inclusion criteria: * able to provide written informed consent * males or females 18 years of age or older * have previously had a primary course of covid-19 vaccine with the most recent dose no less than 3 months previously. * understand and are likely to comply with planned study procedures and be available for all study visits. exclusion criteria * allergy to spikogen vaccine or one of its components, e.g. polysorbate 80. * have received an experimental agent within 30 days prior to the study vaccination or expect to receive another experimental agent during the trial reporting period. * any serious medical, social or mental condition which, in the opinion of the investigator, would be detrimental to the subjects or the study.

inclusion criteria: able to provide written informed consent males or females 18 years of age or older have previously had a primary course of covid-19 vaccine with the most recent dose no less than 3 months previously. understand and are likely to comply with planned study procedures and be available for all study visits. exclusion criteria allergy to spikogen vaccine or one of its components, e.g. polysorbate 80. have received an experimental agent within 30 days prior to the study vaccination or expect to receive another experimental agent during the trial reporting period. any serious medical, social or mental condition which, in the opinion of the investigator, would be detrimental to the subjects or the study.

inclusion criteria: able to provide written informed consent males or females 18 years of age or older have previously had a primary course of covid-19 vaccine with the most recent dose no less than 3 months previously. understand and are likely to comply with planned study procedures and be available for all study visits. exclusion criteria allergy to spikogen vaccine or one of its components, e.g. polysorbate 80. have received an experimental agent within 30 days prior to the study vaccination or expect to receive another experimental agent during the trial reporting period. any serious medical, social or mental condition which, in the opinion of the investigator, would be detrimental to the subjects or the study.