Two groups of individuals are vaccinated with exactly the same dose of a particular vaccine. Assume that the two groups are matched for all the relevant criteria (e.g., age, weight, etc.). One group is allowed to resume normal daily activity, however, another group is sleep deprived for one day after vaccination before resuming normal daily activity. After several weeks, the serum levels of the antibody produced against the vaccine antigen are measured in all individuals participating in the study. Which of the following will be a likely outcome?