Status: Follow-up completed April 2023.  

Population: Adults 30 years and older.  

Disease group: COVID 

Funder: NIHR (National Institute for Health Research)  

Sponsor: University Hospital Southampton NHS Foundation Trust 

Principal Investigator: Prof Paul Heath 

Study Aims 

The COVID-19 virus is always mutating, which allows it to evade the immune response generated by existing vaccines. There are several licensed COVID-19 vaccines in the UK, including new vaccines which target the Omicron variant of the virus. It is currently unknown whether providing more doses of original COVID-19 vaccines (such as BNT162b2, the Pfizer vaccine) would produce better immune responses against the Omicron variant or other COVID-19 variants, or whether giving updated vaccines which are designed to help the body recognise the Omicron variant spike protein (such as mRNA-1273.214) would provide better protection. 

This study is trying to determine the side effects, safety and immune response of giving different fourth COVID-19 vaccine booster doses of BNT162b2 (Pfizer) or mRNA-1273.214 (Moderna Bivalent) to people aged 30 and older who have previously received 3 doses of COVID-19 vaccine.  

What does participating in the study involve?  

The study lasts for 242 days (about 8 months) and involves 5 study visits with blood tests taken at each visit: 

• Screening and vaccination visit: At the first visit, study staff talk to potential participants about the study and what to expect, and about their health and details of previous covid vaccines to check whether they can take part in the study.  If someone is eligible to take part and would like to do so, they are asked to sign a consent form.  
• Participants then have vital signs checked and may have a physical examination by a doctor. They will have baseline antibody blood tests and tests of liver and kidney function for safety. Then, they are randomly allocated to receive either BNT162b2 (Pfizer) or mRNA1273.214 (Moderna Bivalent) as an injection into the arm.  
• Follow-up after vaccination an “e-Diary”, thermometer and tape measure is given to participants to record their temperature and any symptoms they have for 7 days after they have the vaccine, and any symptoms for 21 days after the vaccine.  
• Follow-up visits: participants return to the clinic for four short visits to check they are fine, any changes to their health or medicines and to have blood tests.  
• Participants are told which vaccine they received when they finish the study after their day 242 visit.  

To find out more about the study, visit the study website here: covboost.org.uk