未成年へのｍRNAワクチンは入院を減らすが効果は5ヶ月で消失

2022/3/1にCDCからレポートが出されました。

結論から言うと、
「5歳以上の未成年に対してワクチンは２ヶ月間はかなり有効だが、５ヶ月経つと有効性はかなり失われてしまう」という結果でした。

アメリカでは入院費用がかなり高く、基準も厳しいのですが、2022年2月までに未成年が1万人以上亡くなっているので、入院の基準は下がっているのだろうと思います。（アメリカの事情に関してはあくまで私見です。）

・救急搬送を抑制するワクチン効果

・入院を抑制するワクチン効果
の二つを指標としています。

結果は以下の通り。

　＜5～11歳児＞

2回接種から67日後までは、
・救急搬送に対する有効率が51％、

・入院に対する有効率が74％とかなりの有効率があった。

　＜12～15歳児＞

2回接種67日後までは5～11歳児と同様に良い有効率だった。しかし、

・2回接種から150日以上経つと救急搬送に対する有効率が消失した。

・2回接種から150日以上経っても入院に対する有効率は73％とかなり残っていた。

５ヶ月経つと2回接種では感染を防げないが、重症化は抑制できることを示しています。

　＜16～17歳児＞

2回接種67日後までは5～11歳児と同様に良い有効率だった。

・2回接種から150日以上経っても入院に対する有効率は88％とかなり残っていた。

・追加接種をすると、すぐに救急搬送に対する有効率が復活した。

　以上のことからオミクロン株の感染予防に対して、
・小児に対するワクチン接種は一時的にしか効果がなく、追加接種が必要である。

・追加接種をすればワクチンの有効率が（リンパ球の遺伝子組み換えを介して）速やかに復活する。

オミクロン感染の場合、上気道症状が強く現れ、溶連菌以上に酷い咽頭発赤の症例に出逢います。

オミクロン株の場合、デルタ株に比べて上気道での増殖が7倍で、肺での増殖が1/10程度のため、素早く増え、肺炎を起こさず歩き回ってもらって早く感染させるように適応しています。

私見ですが、何なら咳も少ししか出ないぐらいに進化していくのかも知れません。

以下の家庭では小児に対して、接種を推奨します。

1。高齢者と同居している家庭の小児。

2。免疫不全者と同居している家庭の小児。

3。0〜1歳児の同胞がいる家庭の小児（武漢の頃から一貫して0〜1歳児の肺炎症例は出ています。）

4。色々な活動に制限を受けたくない小児（中学受験や高校受験、競技会、演奏会、卒業式等への参加。）

5。初期免疫を付けておきたい場合（リンパ球の遺伝子組み換えには時間が掛かります。初期免疫2回後に半年空けるのはこのためです。遺伝子を組み換える必要が無い既感染のウイルスでは立ち上がりが早く、抗体が測定感度以下まで下がっていてもB型肝炎等で予防効果を発揮するのはこのためです。また最も強力なのは抗体ではなく、細胞障害性T cellです。）

6。母親が妊婦の場合。（妊婦は一種の免疫不全者です。これは胎児を排除しないためにそうなっています。）

流行が始まるや否や接種するのが最も効果的ですが、上記のいずれも当て嵌まらない場合は、感染対策をして、オミクロン株が去るのを待つことも可能です。

いくら免疫があっても、大量のウイルスを吸い込んだら発症することはあるし、初期に吸い込んだウイルス量は重症度とも関連しますので、気を付けてください。

感染力が強力になった今は、アジア人のハグをしない生活習慣の優位性よりも、住居の狭さの方が不利になっているのです。

これだけの大きな市場になったので、製薬会社も次々に新しいワクチンを開発してくるでしょう。

2022/3/21時点でおそらく日本人の1割程度は（不顕性感染も含めて）感染したでしょうが、まだ感受性のある人は残っていますし、オミクロン株以降は免疫回避のメカニズムを持ったため、病原性を下げながら数回世界中をLoopすると思います。

（2022/3/21 管理者記載）

Effectiveness of COVID-19 Pfizer-BioNTech BNT162b2 mRNA Vaccination in Preventing COVID-19–Associated Emergency Department and Urgent Care Encounters and Hospitalizations Among Nonimmunocompromised Children and Adolescents Aged 5–17 Years — VISION Network, 10 States, April 2021–January 2022

Weekly / March 4, 2022 / 71(9);352–358

https://www.cdc.gov/mmwr/volumes/71/wr/mm7109e3.htm?s_cid=mm7109e3_w

On March 1, 2022, this report was posted online as an MMWR Early Release.

Nicola P. Klein, MD¹; Melissa S. Stockwell, MD^2,3,4; Maria Demarco, PhD⁵; Manjusha Gaglani, MBBS^6,7; Anupam B. Kharbanda, MD⁸; Stephanie A. Irving, MHS⁹; Suchitra Rao, MBBS¹⁰; Shaun J. Grannis, MD^11,12; Kristin Dascomb, MD¹³; Kempapura Murthy, MBBS⁶; Elizabeth A. Rowley, DrPH⁵; Alexandra F. Dalton, PhD¹⁴; Malini B. DeSilva, MD¹⁵; Brian E. Dixon, PhD^11,16; Karthik Natarajan, PhD^4,17; Edward Stenehjem, MD¹³; Allison L. Naleway, PhD⁹; Ned Lewis, MPH¹; Toan C. Ong, PhD¹⁰; Palak Patel, MBBS¹⁴; Deepika Konatham⁶; Peter J. Embi, MD^12,18,19; Sarah E. Reese, PhD⁵; Jungmi Han¹⁷; Nancy Grisel, MPP¹³; Kristin Goddard, MPH¹; Michelle A. Barron, MD¹⁰; Monica Dickerson¹⁴; I-Chia Liao, MPH⁶; William F. Fadel, PhD^11,16; Duck-Hye Yang, PhD⁵; Julie Arndorfer, MPH¹³; Bruce Fireman¹; Eric P. Griggs, MPH¹⁴; Nimish R. Valvi, DrPH¹¹; Carly Hallowell, MPH⁵; Ousseny Zerbo, PhD¹; Sue Reynolds, PhD¹⁴; Jill Ferdinands, PhD¹⁴; Mehiret H. Wondimu, MPH¹⁴; Jeremiah Williams, MPH¹⁴; Catherine H. Bozio, PhD¹⁴; Ruth Link-Gelles, PhD¹⁴; Eduardo Azziz-Baumgartner, MD¹⁴; Stephanie J. Schrag, DPhil¹⁴; Mark G. Thompson, PhD¹⁴; Jennifer R. Verani, MD¹⁴

The efficacy of the BNT162b2 (Pfizer-BioNTech) vaccine against laboratory-confirmed COVID-19 exceeded 90% in clinical trials that included children and adolescents aged 5–11, 12–15, and 16–17 years (1–3). Limited real-world data on 2-dose mRNA vaccine effectiveness (VE) in persons aged 12–17 years (referred to as adolescents in this report) have also indicated high levels of protection against SARS-CoV-2 (the virus that causes COVID-19) infection and COVID-19–associated hospitalization (4–6); however, data on VE against the SARS-CoV-2 B.1.1.529 (Omicron) variant and duration of protection are limited. Pfizer-BioNTech VE data are not available for children aged 5–11 years. In partnership with CDC, the VISION Network* examined 39,217 emergency department (ED) and urgent care (UC) encounters and 1,699 hospitalizations^† among persons aged 5–17 years with COVID-19–like illness across 10 states during April 9, 2021–January 29, 2022,^§ to estimate VE using a case-control test-negative design. Among children aged 5–11 years, VE against laboratory-confirmed COVID-19–associated ED and UC encounters 14–67 days after dose 2 (the longest interval after dose 2 in this age group) was 46%. Among adolescents aged 12–15 and 16–17 years, VE 14–149 days after dose 2 was 83% and 76%, respectively; VE ≥150 days after dose 2 was 38% and 46%, respectively. Among adolescents aged 16–17 years, VE increased to 86% ≥7 days after dose 3 (booster dose). VE against COVID-19–associated ED and UC encounters was substantially lower during the Omicron predominant period than the B.1.617.2 (Delta) predominant period among adolescents aged 12–17 years, with no significant protection ≥150 days after dose 2 during Omicron predominance. However, in adolescents aged 16–17 years, VE during the Omicron predominant period increased to 81% ≥7 days after a third booster dose. During the full study period, including pre-Delta, Delta, and Omicron predominant periods, VE against laboratory-confirmed COVID-19–associated hospitalization among children aged 5–11 years was 74% 14–67 days after dose 2, with wide CIs that included zero. Among adolescents aged 12–15 and 16–17 years, VE 14–149 days after dose 2 was 92% and 94%, respectively; VE ≥150 days after dose 2 was 73% and 88%, respectively. All eligible children and adolescents should remain up to date with recommended COVID-19 vaccinations, including a booster dose for those aged 12–17 years.

VISION Network VE methods have been previously published (7). In brief, eligible medical encounters were defined as ED and UC encounters and hospitalizations among persons aged ≥5 years with a COVID-19–like illness diagnosis^¶ who had received SARS-CoV-2 molecular testing (primarily by reverse transcription–polymerase chain reaction assay) during the 14 days before through 72 hours after the encounter. For adolescents aged 16–17 years, the study period began when COVID-19 vaccines were recommended and became available to persons aged ≥16 years at each study site (April–May 2021).** For children aged 5–11 years and adolescents aged 12–15 years, the study period began 5 weeks after the Pfizer-BioNTech vaccine was recommended for their age group.^†† The dates when the Delta and Omicron variants became predominant (accounted for >50% of sequenced viruses) were determined for each study site based on state and national surveillance data.^§§ Patients were excluded if they 1) were vaccinated before the CDC recommendation date for their age group, 2) received a third dose before booster doses were recommended for their age group, 3) received a booster dose <5 months after dose 2, 4) received 1 or >3 doses of the vaccine, or 5) if <14 days had elapsed since receipt of dose 2 or <7 days since dose 3. Patients who were likely immunocompromised based on diagnosis codes were also excluded.^¶¶ VE was estimated using a case-control test-negative design comparing the odds of a positive SARS-CoV-2 test result between vaccinated (received 2 doses ≥14 days earlier or 3 doses ≥7 days earlier) and unvaccinated (received no doses) patients using multivariable logistic regression models*** (7). VE was not calculated for exposure categories with fewer than 20 encounters or with no SARS-CoV-2 test–positive cases. A statistically significant difference in VE or distributions of vaccination or infection status was indicated by nonoverlapping 95% CIs or standardized mean or proportion differences ≥0.2. All statistical analyses were conducted using R software (version 4.1.2; R Foundation). This study was reviewed and approved by the institutional review boards at participating sites or under a reliance agreement with the Westat, Inc. institutional review board.

Emergency Department and Urgent Care Encounters

Among 39,217 eligible encounters at 306 ED and UC facilities, 23.4%, 46.2%, and 30.3% were among persons aged 5–11, 12–15, and 16–17 years, respectively (Table 1). Most encounters among adolescents aged 12–15 years and 16–17 years occurred during the Delta predominant period (14,491 [79.9%] and 8,800 [74.0%], respectively); among children aged 5–11 years, most (6,424 [70.0%]) occurred during the Omicron predominant period, reflecting differences in the dates when vaccines became available for the respective age groups.

Among children aged 5–11 years, VE of 2 doses received 14–67 days earlier against COVID-19–associated ED and UC encounters was 46% (Table 2). Among adolescents aged 12–15 and 16–17 years, VE of 2 doses 14–149 days earlier against COVID-19–associated ED and UC encounters was 83% and 76%, respectively; VE was significantly lower for 2 doses received ≥150 days earlier (38% and 46%, respectively). Among adolescents aged 16–17 years, VE after receipt of a third dose ≥7 days earlier increased to 86%, significantly higher than the VE of 2 doses received ≥150 days earlier. The number of observations was insufficient to estimate 3-dose VE for adolescents aged 12–15 years. Compared with the Delta predominant period, estimated 2-dose VE for adolescents aged 12–15 and 16–17 years declined significantly once Omicron became the predominant variant: among adolescents aged 16–17 years, VE of 2 doses received ≥150 days earlier against COVID-19–associated ED and UC encounters declined from 77% during Delta predominance to a null VE (–3%) during Omicron predominance; however, effectiveness of a third dose received ≥7 days earlier against COVID-19–associated ED and UC encounters during Omicron predominance was 81%. Among children aged 5–11 years, VE of 2 doses received 14–67 days earlier against COVID-19–associated ED and UC encounters during Omicron predominance was 51%.

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Hospitalizations

Among 1,699 eligible hospitalizations at 164 hospitals, 16.8%, 43.6%, and 39.6% were among children and adolescents aged 5–11, 12–15 and 16–17 years, respectively (Table 3). Most hospitalizations of adolescents aged 12–15 years (613 [82.7%]) and 16–17 years (476 [70.7%]) occurred during Delta predominance, whereas two thirds of hospitalizations among children aged 5–11 years (190 [66.7%]) occurred during Omicron predominance.

Among children aged 5–11 years, estimated VE of 2 vaccine doses received 14–67 days earlier against COVID-19–associated hospitalization was 74%, with wide confidence intervals that included zero (95% CI = –35% to 95%) (Table 2). Among adolescents aged 12–15 and 16–17 years, VE of 2 doses received 14–149 days earlier was 92% and 94%, respectively, and VE of 2 doses received ≥150 days earlier was 73% and 88%, respectively. Differences by time since vaccination were not statistically significant.

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Discussion

In a multistate analysis of 39,217 ED and UC encounters with COVID-19–like illness among nonimmunocompromised patients aged 5–17 years through January 29, 2022, estimates of Pfizer-BioNTech VE against COVID-19–associated ED and UC encounters varied by time since vaccination and by predominant circulating SARS-CoV-2 variant. Among adolescents aged 12–17 years during the full study period including pre-Delta, Delta, and Omicron predominant periods, 2-dose VE estimates were higher (76%–83%) 14–149 days after receipt of a second dose, and significantly lower (38%–46%) at ≥150 days postvaccination. However, a third vaccine dose restored VE against COVID-19–associated ED or UC encounters to 86% among adolescents aged 16–17 years. Among children aged 5–11 years during the full study period, VE of 2 doses (14–67 days earlier) against COVID-19–associated ED or UC encounters was 46%, which was significantly lower than overall estimates for adolescents aged 12–17 years. However, most encounters among children aged 5–11 years occurred during Omicron predominance, when VE significantly declined for adolescents aged 12–17 years. During Omicron predominance, VE of a second dose received 14–149 days earlier was 45% and 34% for adolescents aged 12–15 and 16–17 years, respectively, suggesting that the lower VE observed among children aged 5–11 years was likely driven by the predominant variant rather than differences in VE across age groups. During Omicron predominance, there was no evidence of protection for adolescents aged 12–17 years from 2 doses received ≥150 days earlier; however, a third vaccine restored VE to 81% among adolescents aged 16–17 years.

Receipt of 2 Pfizer-BioNTech vaccine doses in persons aged 12–17 years provided a high level of protection (>90%) against COVID-19–associated hospitalizations within 149 days of receipt of the second dose. VE point estimates for second dose received ≥150 days earlier were 73% to 88%; however, differences by time since vaccination were not statistically significant. Additional data are needed to better understand duration of protection against COVID-19–associated hospitalization in adolescents aged 12–17 years, the protection from 3 doses, and the level of protection among children aged 5–11 years.

These findings are consistent with previously published data showing high effectiveness of the Pfizer-BioNTech vaccine among adolescents before Omicron became the predominant variant (4–6), and with data from adults demonstrating relatively higher protection against more severe outcomes (7). These findings are also consistent with data showing a decline in mRNA VE over time since receipt of the second dose among adolescents and adults (8–10). The findings in this report also align with studies among adults that report lower VEs during Omicron variant predominance (9,10) and an increase in VE after receipt of a third vaccine dose (9,10).

The findings in this report are subject to at least six limitations. First, comparison of VE estimates between age groups should be made with caution because of differences in the timing of vaccine availability and predominant variants when the vaccine became available to different age groups. Second, statistical power for estimating VE against COVID-19–associated hospitalizations was limited, resulting in wide CIs for some groups, particularly children aged 5–11 years. Third, among adolescents aged 16–17, the estimated 3-dose VE was based on a relatively short period after vaccination. Fourth, despite adjustments to balance the differences between unvaccinated and vaccinated persons, unmeasured and residual confounding (e.g., mask use and physical distancing) might have biased the estimates. Fifth, genetic characterization of patients’ viruses was not available, and Delta and Omicron predominance periods were based on surveillance data. Finally, although the facilities in this study serve heterogeneous populations in 10 states, the findings might not be generalizable to the U.S. population.

This report provides real-world evidence of protection by the Pfizer-BioNTech vaccine against COVID-19–associated ED and UC encounters and hospitalizations among children and adolescents aged 5–17 years and supports the role of third (booster) doses in maintaining high levels of VE in the setting of Omicron predominance. All eligible children and adolescents should remain up to date with recommended COVID-19 vaccinations, including a booster dose for those aged 12–17 years.

2021年12月9日から2022年2月20日までの間に、v-safeは、12〜15歳の人に投与された1,952、16〜17歳の人に投与された1,466を含む、青年に投与された合計3,418のファイザー-BioNTechブースター用量を記録しました。

局所注射部位反応（2,802; 82.0％）
および全身反応（2,659; 77.8％）は、すべての青年に対する追加免疫ワクチン接種後の1週間に頻繁に報告されました（表1）。

最も頻繁に報告された副作用は、
注射部位の痛み（2,736; 80.0％）、
倦怠感（1,998; 58.5％）、
頭痛（1,911; 55.9％）、
筋肉痛（1,578; 46.2％）でした。
反応はほとんど軽度から中等度の重症度であり、ワクチン接種の翌日に最も頻繁に報告されました。
局所注射部位反応は、追加免疫投与（82.0％）後に投与2（77.8％）よりも一般的に報告され（p <0.001）、全身反応は追加免疫投与（77.8％）および投与2（77.2％）後に同様に報告されました（p = 0.48）（図）。

ブースター用量ワクチン接種の翌週に、青年の20.0％（682）が学校や仕事に通うことができないと報告されました。伝えられるところによると、青年の約0.9％（32）は、追加免疫ワクチン接種後の1週間に医療を受けました。ほとんど（15; 0.4％）のケアは、診療所の予約を通じて受けられました。 1人（0.03％）の青年は、新たに発症した片頭痛の治療のために追加免疫ワクチン接種後の1週間に病院で治療を受けました。入院がワクチン接種の結果であったかどうかは判断できませんでした。ブースター投与を受けた後（25.8％）は、投与2後（28.8％）よりも日常の活動ができないことが報告される頻度は低かった（p <0.001）（図）。それぞれ9.4％）（p <0.001）。ブースター用量の受領後、医療の受領は、用量2よりも頻繁に報告されました（それぞれ0.9％および0.6％）。ただし、差は統計的に有意ではありませんでした（p = 0.12）。

Safety Monitoring of COVID-19 Vaccine Booster Doses Among Persons Aged 12–17 Years — United States,
December 9, 2021–February 20, 2022

On March 1, 2022, this report was posted online as an MMWR Early Release.

Anne M. Hause, PhD¹; James Baggs, PhD¹; Paige Marquez, MSPH¹; Winston E. Abara, MD¹; Babatunde Olubajo, MS¹; Tanya R. Myers, PhD¹; John R. Su, MD¹; Deborah Thompson, MD²; Julianne Gee, MPH¹; Tom T. Shimabukuro, MD¹; David K. Shay, MD¹

Summary

What is already known about this topic?

Adults aged ≥18 years reported adverse reactions less frequently after receipt of a homologous Pfizer-BioNTech COVID-19 booster dose than after the second primary dose.

What is added by this report?

Among persons aged 12–17 years, reactions after Pfizer-BioNTech booster vaccination were generally mild to moderate and transient; the frequency of local and systemic reactions reported to v-safe after a booster dose were equal to or slightly higher than after the second primary dose. Myocarditis was less frequently reported after a booster dose than a second primary dose.

What are the implications for public health practice?

Health care providers, parents, and adolescents should be advised that local and systemic reactions are expected among adolescents after a homologous Pfizer-BioNTech booster vaccination and that serious adverse events are rare.

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As of February 20, 2022, only BNT162b2 (Pfizer-BioNTech) COVID-19 vaccine has been authorized for use in persons aged 12–17 years in the United States (1). The Food and Drug Administration (FDA) amended the Emergency Use Authorization (EUA) for Pfizer-BioNTech vaccine on December 9, 2021, to authorize a homologous* booster dose for persons aged 16–17 years ≥6 months after receipt of dose 2 (1). On January 3, 2022, authorization was expanded to include persons aged 12–15 years, and for all persons aged ≥12 years, the interval between dose 2 and booster dose was shortened to ≥5 months (1). To characterize the safety of Pfizer-BioNTech booster doses among persons aged 12–17 years (adolescents), CDC reviewed adverse events and health impact assessments during the week after receipt of a homologous Pfizer-BioNTech booster dose reported to v-safe, a voluntary smartphone–based safety surveillance system for adverse events after COVID-19 vaccination, and adverse events reported to the Vaccine Adverse Event Reporting System (VAERS), a passive vaccine safety surveillance system managed by CDC and FDA. During December 9, 2021–February 20, 2022, approximately 2.8 million U.S. adolescents received a Pfizer-BioNTech booster dose.^† During this period, receipt of 3,418 Pfizer-BioNTech booster doses were reported to v-safe for adolescents. Reactions were reported to v-safe with equal or slightly higher frequency after receipt of a booster dose than after dose 2, were primarily mild to moderate in severity, and were most frequently reported the day after vaccination. VAERS received 914 reports of adverse events after Pfizer-BioNTech booster dose vaccination of adolescents; 837 (91.6%) were nonserious and 77 (8.4%) were serious. Health care providers, parents, and adolescents should be advised that local and systemic reactions are expected among adolescents after homologous Pfizer-BioNTech booster vaccination, and that serious adverse events are rare.

V-safe is a voluntary, smartphone–based U.S. active safety surveillance system established to monitor adverse events after COVID-19 vaccination (https://vsafe.cdc.gov/en/). The v-safe platform allows current registrants to report receipt of a booster dose of COVID-19 vaccine and new registrants to enter information about all doses received. Registrants aged ≤15 years must be enrolled by a parent or guardian. Health surveys are sent daily during the first week after administration of each dose and include questions about local injection site and systemic reactions and health impacts.^§ CDC’s v-safe call center contacts registrants who indicate that medical care was sought after vaccination and encourages completion of a VAERS report, if indicated.

VAERS is a U.S. national passive vaccine safety surveillance system managed by CDC and FDA that monitors adverse events after vaccination (2). VAERS accepts reports from health care providers, vaccine manufacturers, and members of the public.^¶ VAERS reports are classified as serious if there are any reports of hospitalization, prolongation of hospitalization, life-threatening illness, permanent disability, congenital anomaly or birth defect, or death.** VAERS staff members assign Medical Dictionary for Regulatory Activities (MedDRA) preferred terms to the signs, symptoms, and diagnostic findings in VAERS reports.^†† Serious reports to VAERS were reviewed by CDC physicians to form a clinical impression based on available data. Reports of myocarditis and pericarditis, rare adverse events that have been associated with mRNA-based COVID-19 vaccines (3), after receipt of a booster vaccine were identified by a search for selected MedDRA preferred terms; CDC staff members attempted to collect information about clinical course and determined whether the CDC myocarditis case definition was met.^§§

This report assessed local and systemic reactions and health impacts reported during the week after vaccination among adolescent v-safe registrants who received a homologous Pfizer-BioNTech booster dose ≥5 months after completion of their primary series during December 9, 2021–February 20, 2022. The odds of reporting an adverse reaction or health impact after dose 2 and booster dose were compared using a multivariable generalized estimating equations model; p<0.05 was defined as statistically significant.^¶¶ VAERS reports for adolescents who received a Pfizer-BioNTech booster dose during December 9, 2021–February 20, 2022, were described by serious and nonserious classification, demographic characteristics (i.e., sex and age), and MedDRA preferred terms.*** Reporting rates for myocarditis were stratified by sex and age group. SAS software (version 9.4; SAS Institute) was used to conduct all analyses. These surveillance activities were reviewed by CDC and conducted consistent with applicable federal law and CDC policy.^†††

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Review of v-safe Data

During December 9, 2021–February 20, 2022, v-safe recorded a total of 3,418 Pfizer-BioNTech booster doses administered to adolescents, including 1,952 administered to persons aged 12–15 years and 1,466 to those aged 16–17 years. Local injection site reactions (2,802; 82.0%) and systemic reactions (2,659; 77.8%) were frequently reported during the week after booster dose vaccination for all adolescents (Table 1); the most frequently reported adverse reactions were injection site pain (2,736; 80.0%), fatigue (1,998; 58.5%), headache (1,911; 55.9%), and myalgia (1,578; 46.2%). Reactions were mostly mild to moderate in severity and most frequently reported the day immediately after vaccination. Local injection site reactions were more commonly reported after booster dose (82.0%) than dose 2 (77.8%) (p<0.001), and systemic reactions were similarly reported after booster dose (77.8%) and dose 2 (77.2%) (p = 0.48) (Figure).

In the week after booster dose vaccination, 20.0% (682) of adolescents were reported as being unable to attend school or work. Approximately 0.9% (32) of adolescents reportedly received medical care during the week after booster dose vaccination; most (15; 0.4%) care was received via a clinic appointment. One (0.03%) adolescent received care at a hospital during the week after booster dose vaccination for treatment of a new onset migraine; whether hospitalization was the result of vaccination could not be determined. Inability to perform daily activities was less frequently reported after receipt of the booster dose (25.8%) than after dose 2 (28.8%) (p<0.001) (Figure), whereas inability to work or attend school was more frequently reported (20.0% and 9.4%, respectively) (p<0.001). Receipt of medical care was more frequently reported after receipt of the booster dose than dose 2 (0.9% and 0.6%, respectively); however, the difference was not statistically significant (p = 0.12).

Review of VAERS Data

During December 9, 2021–February 20, 2022, VAERS received and processed 914 reports of adverse events after receipt of a Pfizer-BioNTech booster dose for adolescents; the median age was 16 years, and 459 (50.2%) reports were for adolescent girls. Most VAERS reports were for nonserious events (837; 91.6%); the most commonly reported nonserious events included product storage error (123; 14.7%), dizziness (100; 12.0%), and syncope (87; 10.4%) (Table 2). Sixty-four preliminary reports of myocarditis were received, among which 47 were considered serious; 32 (68.1%) of these reports were confirmed by provider interview or medical record review to meet the CDC working definition of myocarditis. All 32 reports were among adolescent boys and 27 (84.4%) patients were hospitalized; as of February 20, 2022, all had been discharged, 18 had recovered, and nine were recovering. Among adolescent boys, the reporting rate for confirmed cases of myocarditis after Pfizer-BioNTech booster vaccination was 11.4 per 1 million booster doses administered. No deaths were reported to VAERS.

Discussion

This report provides findings from v-safe and VAERS data collected during the first 7–11 weeks of administration of homologous Pfizer-BioNTech booster doses to persons aged 12–17 years, during which time approximately 2.8 million booster doses were administered. Among adolescents, reports to v-safe and VAERS after receipt of a booster dose were generally similar to those previously described after a primary series dose, reinforcing that vaccination among this population is safe (4,5). Health care providers, parents, and adolescents should be advised that local and systemic reactions are expected among adolescents after Pfizer-BioNTech booster vaccination and that serious adverse events are rare.

Reports to v-safe after receipt of a booster dose in an adolescent were generally similar to those previously described for persons aged ≥18 years who received a homologous booster dose of Pfizer-BioNTech vaccine (6,7); however, reactions among adolescents were reported to v-safe with equal or slightly higher frequency after receipt of a booster dose than after dose 2. Reactions reported after both dose 2 and booster dose vaccination were mostly mild to moderate in severity. Most were reported the day after vaccination. Inability to attend school was more frequently reported after a booster dose than after dose 2; however, for many in this age group, receipt of dose 2 occurred during a period of remote learning or summer vacation, which might have affected reporting. Hospitalization in the week after booster dose vaccination was reported for one adolescent with new onset migraine; whether hospitalization was the result of COVID-19 vaccination could not be determined.

Most (91.6%) reports to VAERS for adolescents after a Pfizer-BioNTech booster dose were nonserious and generally similar to those reported for this age group after primary series vaccination (4). The most common adverse events reported to VAERS in this age group were administration errors and events, including dizziness, related to syncope, a vasovagal response to vaccination that is common among adolescents after any vaccination (8). Most reports of administration errors mentioned that no adverse event was associated with receipt of an incorrect dose.

Among the 64 VAERS reports of myocarditis, a rare adverse event that has been associated with mRNA-based COVID-19 vaccines (3), after Pfizer-BioNTech booster dose vaccination among adolescents, 32 cases were confirmed at the time of this report. The reporting rate of confirmed cases of myocarditis among adolescent boys after Pfizer-BioNTech booster dose vaccination (11.4 per 1 million doses administered) was lower than for dose 2 Pfizer-BioNTech vaccination for boys aged 12–15 years (70.7 per 1 million doses administered) or 16–17 years (105.9 per 1 million doses administered) (3). CDC will follow up on myocarditis reports at 3–6 months after onset to assess health and functional status.

The findings in this report are subject to at least four limitations. First, v-safe is a voluntary program; therefore, data might not be representative of the vaccinated population. Second, it is possible that vaccinees who experience an adverse event could be more likely to respond to v-safe surveys. Third, as a passive surveillance system, VAERS is subject to reporting biases and underreporting, especially of nonserious events (2). Finally, assessment of myocarditis reports to VAERS is ongoing, and counts are subject to change.

The Advisory Committee on Immunization Practices recommends that all persons aged ≥12 years receive a booster dose of COVID-19 vaccine ≥5 months after the second dose of the mRNA vaccine primary series (9). Preliminary safety findings for booster doses among adolescents are generally similar to those reported after a primary series in this age group. Health care providers, parents, and adolescents should be advised that local and systemic reactions are expected among adolescents after homologous Pfizer-BioNTech booster vaccination, and that serious adverse events are rare. CDC and FDA will continue to monitor vaccine safety and will provide updates as needed to guide COVID-19 vaccination recommendations.