Aim This randomized controlled experimental study was conducted to determine the effect of ShotBlocker® and manual pressure application on pain in the application of Conjugated Pneumococcal Vaccine (PCV).

The following hypotheses were determined for the study; Hypothesis 1: Pain scores of infants are lower in the manual pressure group than in the control group during the administration of PCV.

Hypothesis 2: Pain scores of infants are lower in Shotblocker® group than in the control group during the administration of PCV.

Hypothesis 3: Manual pressure is more effective than Shotblocker® in infants to reducing pain during the administration of PCV.

The study was carried out at three family health centers, all with the same nurse administering care. Infant who were 4 months old and scheduled to receive the PCV vaccine were eligible for participation. The data were collected using a questionnaire form and the Neonatal Infant Pain Scale (NIPS).

A standard procedure was followed for all infants, which included bringing the infant and mothers into the vaccination room, providing information about the vaccine, introducing the researcher, and obtaining informed consent. Infants were assigned to groups based on randomization. To control factors related to the application process (such as injection technique and communication approach), vaccines were administered by same experienced nurse working at the family center where the research was conducted.

A video camera with a 5X optical zoom support (Samsung M51 brand smartphone) was used to record vaccine injections. It was placed on a tripod across the stretcher where the infants were vaccinated. Each infant was recorded for during vaccination, and 2 min after vaccination.

Written approval was obtained from the Ethics Committee (2021/279) and institution where the study was conducted (E-79593712-605.99). The nurse researcher informed infants' mothers about the study. Upon agreement from mothers, written consent forms were obtained.

Data were analyzed using SPSS for Windows version 25.0 (IBM, Armonk, NY). Numeric variables are presented as counts, percentages, means, standard deviations, and min-max values. The assumption of normal distribution was checked with the Shapiro-Wilk test, and the assumption of homogeneity of variances was controlled with the Levene test. To compare pain scores after vaccination, a paired sample t-test was used. In cases where the data showed a normal distribution and there were more than two independent groups, a one-way analysis of variance (ANOVA) test was employed. A significance level of p < .05 was considered statistically significant.

Inclusion Criteria:

• Infant who were 4 months old
• who receive the pneumococcal conjugate vaccine receive
• healthly infant, free from systemic illnesses
• accompanied by their mothers
• attending the center for routine vaccination

Exclusion Criteria:

• who have serious congenital malformations
• who have neurodevelopmental delays
• who have serious congenital malformations
• who have febrile conditions
• who have a history of circulatory or peripheral vascular issues
• who had taken sedatives, hypnotics, or systemic pain relievers within the last 6 hours
• infant who cried before receiving the vaccine

Infants who met the inclusion criteria and were scheduled for the PCV vaccine injection were assigned to one of three groups: Shotblocker®, manual pressure, or a control group (which received the standard injection technique). To address gender differences, infants were first categorized by gender and then randomly assigned to the three groups using block randomization. To ensure fairness and minimize bias, labels for each group (Shotblocker®, manual pressure, and control) were written on papers of the same color and shape, placed into separate pink and blue boxes. During the vaccination process, the group assignment was determined by a lottery that the mother drew from just before the procedure. Mothers of girls were instructed to draw from the pink box, while mothers of boys drew from the blue box. Each group consisted of 34 infants, with an equal distribution of 17 females and 17 males.