key: cord-1029182-flrjbyms
authors: Shinozuka, Jun; Hata, Michiaki; Eguchi, Hiromi; Mori, Masahiro; Eguchi, Mitsunori; Fukui, Mototaka; Sai, Natsuki; Imashuku, Shinsaku; Sueyoshi, Atsushi
title: COVID-19 vaccination: effective utilization of low dead space (LDS) syringes
date: 2021-09-29
journal: Int J Infect Dis
DOI: 10.1016/j.ijid.2021.09.068
sha: 82a133b7dcaa22a2b413d9e88c54217d2b11ce2f
doc_id: 1029182
cord_uid: flrjbyms

nan

In the spring 2021, the only available vaccine for COVID-19 was the Pfizer-BioNTech mRNA COVID-19 vaccine (Polack et al., 2020) , which was in limited supply in Japan.

Also, it was difficult to procure specialized low dead space (LDS) syringes that can extract the full six doses from each vial of the Pfizer vaccine. When the Government provided the Pfizer vaccine to health care workers in our hospital, 1,242 candidates applied for their first shot. However, the use of regular syringes with high dead space meant that only five of the six doses could be extracted from each vial. Thus, the number of doses was insufficient to vaccinate every applicant. Therefore, we looked for alternative ways of using available syringes to extract all of the vaccine doses from each vial.

Institutional review board approval: The following vaccination program was approved by the institutional review board of Uji-Tokushukai Medical Center. Also, written informed consent was obtained from every vaccine recipient.

Applicants for COVID-19 vaccine and the vials provided. The hospital received 195 vials of Pfizer vaccine to vaccinate 1,242 health care workers; however, using regular syringes meant that there was enough vaccine for only 975 applicants. Syringes. Insulin syringes (BD; 29G), a type of LDS syringe used routinely for diabetic patients, have the lowest dead space (Figure 1) ; use of these syringes allowed extraction of seven doses per vial. However, the length of needle attached to the insulin syringe was only 12.7 mm. Since the Pfizer vaccine must be administered intramuscularly, there was some concern about whether this type of syringe can deliver vaccine into the shoulder muscle effectively.

Assessment of thickness of subcutaneous fat at the inoculation site. Each recipient underwent routine ultrasound (US) examination to assess the thickness of the subcutaneous fat (i.e., the distance from the skin surface to the muscle) at the injection site in the shoulder muscle.

Each vial of the Pfizer vaccine contained 0.45 mL, which was diluted with 1.8 mL of saline to yield a total volume of 2.25 mL. One shot contained 30 µg of vaccine product (0.3 mL/dose) per manufacturer's recommendation.

From one vial, with a combination of insulin syringes and a regular syringe, 6 doses (each 0.3 mL) with insulin syringes and one dose (0.3 mL) with a regular syringe, a total of 7 doses could be extracted, which were used for 1003 recipients (Group A, Table   1 ). On the other hand, with use of a regular syringes only, 5 doses (each 0.3mL) could be extracted, which were applied for 239 recipients (Group B, Table 1 ).

Inoculation. Based on the above data, recipients with subcutaneous fat ≦10 mm thick were inoculated using insulin syringes, and those with subcutaneous fat >10 mm thick were inoculated with regular syringes (BD; 25G) with a long needle (25 mm). Two shots of vaccine (each at 0.3 ml) were given 3 weeks apart (1 st and 2 nd shots). Statistical analysis. Data were assessed using the Chi-square test. Statistical significance was set at P < 0.05.

As summarized in Table 1 , 1,242 applicants aged from 19 to 82 years received the vaccine, which was delivered using two types of syringes. Based on the thickness of the There was no significant difference in the incidence of ARs between groups A and B after the 1 st and 2 nd shots (p>0.05, Table 1 ). However, the incidence of ARs after the 2 nd shot was significantly higher than that after the 1 st shot (p<0.05). Only one case of anaphylaxis (Level 3 according to the Brighton criteria) was observed at the time of 1 st shot in group B. In terms of antibody induction, both groups elicited significantly high anti-spike-IgG antibody titers (>95% seropositivity with the cut-off 4000 AU/mL) and there was no significant difference in antibody positivity rates between groups A and B (p>0.05, Table 1 ). Although anti-spike-IgG antibodies at baseline were not tested prior to vaccination, seropositivity in the vaccine recipients was considered due to vaccination effect, under the consideration of a low seropositive prevalence 7 (5.3 %-5.8 % in general population, https://www.pref.kyoto.jp › kentai › corona › pcrkensa) in the spring of 2021 in Kyoto and in assessing from our anti-spike-IgG negative and positive control values (see footnotes of Table 1 ). No individuals in either group had a symptomatic infection with COVID-19 after the 2 nd shot. Therefore, we concluded that COVID-19 vaccination using LDS-insulin syringes was as effective as that delivered using regular syringes. However, our ingenuity here may limit only for the occasions where sufficient doses of COVI-19 vaccine and suitable syringes were not procured. In cases insulin LDS syringes were applied for inoculation, US measurements of the recipients' subcutaneous fat, if possible, is ideal. In summary, because the COVID-19 vaccine is very precious, effective utilization of available vaccines is highly recommended.

Schematic illustration showing a regular syringe with high dead space and a low dead space (LDS)-type insulin syringe. 

Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine

Anaphylaxis: case definition and guidelines for data collection, analysis, and presentation of immunization safety data

The authors thank all medical staffs involved in the COVID-19 vaccine program at Uji-Tokushukai Medical Center. 

The authors declare no conflicts of interest.