疫苗接種率正在下降，人們拒絕的不僅僅是 COVID-19 疫 – 愛滋防治宣導-財團法人台灣紅絲帶基金會

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疫苗接種率正在下降，人們拒絕的不僅僅是 COVID-19 疫

疫苗接種率正在下降，人們拒絕的不僅僅是 COVID-19 疫苗

社會對兒童疾病的最佳防禦正在減弱。需要做些什麼來幫助它恢復？

資料來源：Michael Eisenstein/OUTLOOK/2022 年 12 月 19 日/自然/ 財團法人台灣紅絲帶基金會編譯

圖片來源：Oli Winward

疫苗為傳染病提供了有力的防護，這些傳染病曾經造成大量死亡率和發病率，尤其是在兒童中。在 COVID-19 大流行之前的幾年裡，這件盔甲已經形成了縫隙。但在疫苗接種率停滯不前的情況下，這場大流行病就像一把霰彈槍，在人類防禦麻疹等可預防疾病的防禦系統上打出更多漏洞。

《自然》期刊展望中的一部分：兒童健康

允許這些感染蔓延的風險是顯而易見的。辛巴威目前正在努力遏制一場大規模的麻疹疫情，該疫情在 4 月至 10 月期間奪去了 750 多名兒童的生命。經過數十年的成功消除，脊髓灰質炎病毒最近在美國重新出現，促使紐約進入緊急狀態。

疫苗接種率的下降在一定程度上是大流行病本身的直接後果，大流行病導致公共衛生服務嚴重中斷並轉移了資源。但這不僅僅是獲得疫苗的危機。全球公共衛生應對措施的失敗和不公平，加上大流行病的政治化，也削弱了人們對協調和開展免疫工作的機構和人員的信心。

因此，全球疫苗接種率已降至 2008 年以來的最低點——要重回正軌可能很困難。瑞士日內瓦世界衛生組織 (WHO) 免疫計畫負責人凱特·奧布賴恩 (Kate O’Brien) 說：「我們談論的是數千萬人的生命受到威脅」。重建在大流行病期間失去的信任將是遏制本可預防疾病在全球蔓延的關鍵一步。

動量脫軌

在 21 世紀的大部分時間裡，疫苗接種工作都朝著正確的方向發展，延續了 1970 年代開始的趨勢。 1974 年，世界衛生組織啟動了擴大免疫規劃，其使命是確保全世界都能獲得針對包括麻疹在內的六種致命傳染病的疫苗。到2014年，全球許多疫苗可預防疾病的疫苗覆蓋率總體已達到85%，世界部分地區取得了顯著成效。奧布賴恩說，到 2015 年，美洲已經消滅了脊髓灰質炎、麻疹和風疹，儘管這些疾病繼續在其他地方傳播。

但疫苗接種是一個持續的過程，不是一蹴而就的，進一步的進展證明是一個挑戰（見「失去的進展」）。西雅圖華盛頓大學健康指標與評估研究所的流行病學家喬納森·莫塞爾 (Jonathan Mosser) 說，在大流行之前的幾年裡，「我們確實看到許多這些歷史悠久的疫苗的覆蓋面停滯不前」。此外，地區或國家層面的統計數據可以掩蓋地方層面相當大的不平等。位於開普敦的南非醫學研究委員會的疫苗學家 Duduzile Ndwandwe 指出，儘管南非常規兒童疫苗的大流行前覆蓋率約為 85%，但該國內部存在很大差異。「東開普省、林波波省和姆普馬蘭加省等最貧窮的省份並沒有那麼好」，Ndwandwe 說。「他們將接近 60-70%」。這遠遠低於 90% 或更多，這通常被認為是強有力地控制疫苗可預防疾病所必需的。

失去進展：經過多年穩步增長後，12 個月至 23 個月兒童的麻疹疫苗接種率在 COVID-19 大流行之前的幾年裡停滯不前。自大流行以來，過去十年的進步基本上被抹去了。資料來源：世界銀行

到 2019 年，麻疹疫情以驚人的頻率突然出現，並構成了真正的全球威脅。「2019 年爆發的疫情規模巨大，我們看到死亡人數大幅增加」，澳大利亞紐卡斯爾大學研究公共衛生的戴維·杜爾海姆 (David Durrheim) 說。「我們看到各國不堪重負」。那一年，全球有超過 200,000 例麻疹死亡病例，比 2016 年的總數增加了 50%。造成這種倒退的原因有很多，包括用於疫苗接種計畫的資源不足以及一些國家對免疫接種工作的重視程度較低。但全球範圍內對疫苗猶豫不決的上升也是一個重要因素，世界衛生組織將這一趨勢列為 2019 年全球健康面臨的十大威脅之一。

這種危險的情況促使世衛組織制定了 2030 年免疫議程，該議程於 2020 年 4 月宣布，目標是實現 90% 的標準兒童疫苗全球覆蓋率，同時加快向低收入國家引入新的免疫接種。

延遲的劑量

但在該組織正式宣布 COVID-19 為大流行病僅幾週後，就宣布了這一消息。「它關閉了一切」，奧布萊恩說。「與去年同月接種的劑量相比，你只會在 2020 年 4 月、5 月和 6 月看到這種絕對直線下降」。

在大流行的第一年，常規的兒科疫苗接種受到了嚴重打擊。 Mosser 和他的同事梳理了來自 WHO 等來源的數據，並估計在 2020 年，COVID-19 導致 800 萬至 900 萬例兒童錯過接種麻疹、風疹和白喉等疾病的常規疫苗。迄今為止，非洲和亞洲部分地區的比率下降幅度最大，但其他地區的高收入國家在大流行開始時也出現了下降。

這種早期影響在很大程度上直接歸因於為遏制 SARS-CoV-2 病毒的傳播而採取的強有力措施，許多司法管轄區限制旅行、關閉學校並限制獲得非緊急醫療服務。但醫療保健提供者也在為有限的能力而苦苦掙扎。「資源和專業知識從許多衛生保健部門（包括免疫系統）轉移到應對 COVID 上」，Mosser 說。即使在安排就醫時沒有正式障礙，社會和心理因素也會發揮作用，進一步破壞及時接種疫苗。 Ndwandwe 說：「COVID 甚至讓人害怕接觸醫療服務」。

這場大流行還使許多針對資源有限環境中兒童的有針對性的疫苗接種活動戛然而止。世界衛生組織的一項分析發現，到 2020 年 5 月，計畫中的 183 項疫苗接種活動中有近 60% 被取消或推遲。

隨著 COVID-19 的直接衝擊過去，常規的兒童疫苗接種工作又開始加速——尤其是在高收入國家。但即使在富裕地區，這場大流行病也加劇了醫療保健系統中的結構性不平等，並使許多服務不足的社區無法獲得疫苗可預防疾病的保護。例如，Durrheim 說，「在紐西蘭，麻疹的第二劑疫苗覆蓋率已經下降到略高於 80%，而毛利人、原住民和太平洋島民的下降幅度更是不成比例」。

在低收入國家，反彈更加不平衡。到 2021 年底，世衛組織在大流行前安排的疫苗接種活動中有 16% 已被取消或仍處於暫停狀態，導致全球漏掉 3.82 億劑。 O’Brien 還指出，有些自相矛盾的是，醫療保健界對提供針對 COVID-19 的免疫接種的高度關注，有時意味著標準的兒童疫苗系列被擱置一旁，以支持實現大流行控制。「這就是為什麼在 2021 年，我們沒有看到我們認為會發生的復甦」，她說。儘管如此，包括尼泊爾、孟加拉國、泰國和巴基斯坦在內的一些國家在過去三年中透過在資源有限的情況下繼續優先進行常規兒童免疫接種，得以保持穩定並保持高覆蓋率。

失去信心

但收復疫苗覆蓋率失地的努力也受到大流行的其他遺留問題的威脅，包括對政府和公共衛生機構的信任度下降——COVID-19 疫苗的出現加劇而不是減弱了這一趨勢。

早在 COVID-19 疫苗甚至可用於兒童之前，它們就已成為爭議的導火線——最引人注目的是但不限於美國。馬里蘭州巴爾的摩市約翰霍普金斯大學的疫苗學家丹尼爾薩爾蒙認為，人們對疫苗的一些問題可以追溯到它在「曲速行動」中的起源。這個耗資數十億美元的美國公私合作夥伴關係旨在在前所未有的時間框架內開發大流行疫苗。他特別批評該計畫強調速度，而沒有圍繞建立公眾接受度進行並行規劃。「你必須讓人們想要疫苗」，薩蒙說。「但那不是他們的目標」。

一名擴大免疫計畫的工作人員在巴基斯坦 Nowshera 的一家衛生診所準備麻疹疫苗。圖片來源：WHO/Asad Zaidi

在美國應對 COVID-19 已經政治化的背景下，未能引起公眾對 COVID-19 疫苗的信任和熱情——尤其是那些使用相對較新的基於信使 RNA 的技術開發的疫苗——造成了難以解決的問題 . 康涅狄克州紐黑文市耶魯大學全球健康研究所所長薩阿德·奧默 (Saad Omer) 在談到美國新聞頻道時說：「許多人最初認為，透過上 CNN 並皺起眉頭，我們就能說服人們接種疫苗」。「這不是疫苗說服的方式」。當成年人對疫苗缺乏信心時，他們為孩子接種疫苗的可能性就會直線下降。截至 2022 年 10 月，美國祇有 37% 的符合條件的兒童接受過哪怕一劑疫苗。

儘管在大流行之前，大多數美國父母都讓他們的孩子接種多種疾病的疫苗以遵守學校的規定，但薩蒙估計，三分之一到四分之一的人對這些常規兒童疫苗接種的安全性和必要性表示嚴重擔憂。「我擔心的是那些守口如瓶的人，那些可能被推到邊緣的人」，他說。在 COVID-19 的背景下，這個問題變得更加突出。例如，幾份報告描述了接受多針 mRNA 疫苗的青春期男孩心臟組織發炎的病例——一種稱為心肌炎的病症。

儘管這些病例很少見、病情輕微並且往往會自行解決，但這種安全擔憂可能會改變已經猶豫不決的父母接種疫苗的可能性。將這些副作用與 COVID-19 本身帶來的更大威脅聯繫起來，對政府和公共衛生組織來說是一個挑戰。「公共衛生人員需要保持透明」，珀斯西澳大利亞大學疫苗接種政策研究人員 Katie Attwell 說。「他們確實需要談論風險，他們需要將風險背景化」。

對 COVID-19 注射的擔憂在多大程度上加劇了人們對其他疫苗的猶豫，目前尚不清楚。但一些研究疫苗接種情況的人已經開始擔心了。「獲取數據需要時間，但如果我們看到常規疫苗接種量大幅下降，我不會感到驚訝——尤其是在那些真正拒絕接種 COVID 疫苗的人群中」，Salmon 說。 Omer 的研究已經發現了一些早期跡象，表明美國孕婦對破傷風、白喉和百日咳疫苗的接種率有所下降。儘管這些仍然是初步調查結果，但他說，「我擔心的是，這有點像是一座冰山，我們才剛剛開始看到冰山一角」。

西方世界對疫苗的看法也有明顯的政治因素。 2021 年對 1,745 名美國父母進行的一項調查發現，投票給共和黨的父母放棄給孩子接種 COVID-19 疫苗的可能性是民主黨父母的兩倍多。至少對於某些人來說，疫苗接受度與政治認同密切相關。對歐洲疫苗信心的分析發現，對疫苗的猶豫和拒絕與右翼民粹主義政治密切相關。

這種不信任仍有可能在全球蔓延。倫敦衛生與熱帶醫學學院的人類學家海蒂·拉爾森 (Heidi Larson) 表示，「顯然存在一個全球協調的、非常深入的負面網絡」，利用大流行時期的不信任透過社交網絡例如推特和臉書傳播和促進更廣泛的反疫苗議程。在南非，Ndwandwe 發現這種疫苗猶豫主要在更富裕的社區傳播，這些社區有時間和資源在互聯網上查找信息和錯誤信息。「TikTok 是我見過的最危險的平台之一」，她說。「這就是很多事情發生的地方」。Omer 說，在無法方便地取得互聯網的較貧窮社區中，談話很容易被無線電廣播、宗教領袖或海報活動所推動。

克服猶豫

然而，將對疫苗猶豫不決簡單地歸因於對科學的恐懼或誤解是錯誤的。作為倫敦衛生與熱帶醫學院的非營利性計畫疫苗信心計畫的負責人，拉爾森已經能夠梳理出決定是否接種疫苗的一些動機。根據她對最近來自非洲和歐盟的未發表數據的初步評估，許多人之所以猶豫不決，僅僅是因為他們看不到為他們所認為並不真正關心的疾病去接種疫苗的重要性。

這與 Ndwandwe 在南非的經歷是一致的。她說，已經經常接觸醫療系統的母親們往往相信醫生或護士的指導，即免疫接種很重要，即使在大流行的高峰期也是如此。但在較貧窮的社區，情況有所不同，人們在尋求常規照護時往往需要做出相當大的權衡。「你在這裡談論的是相互競爭的優先事項」，她說。「我要不要跑 10 公里去診所坐一整天，而不是去做一份能給我錢並養活我孩子的工作」？

更多來自 Nature Outlooks-《自然》期刊展望

對曾經信任的當局的信心削弱也起到了重要作用。但這可能出於多種原因——從西方國家惡意的政治爭論到向世界上最貧窮的國家提供 COVID-19 疫苗的長期拖延。拉爾森說：「如果說全球衛生真的對一個地區失去了很多信任，那就是非洲」。「我們讓他們大失所望，這一點不會被遺忘」。

對疫苗的猶豫或拒絕往往是政治、宗教、社會和文化因素以及對個人具有高度特異性的個人考慮的複雜組合的結果。這就需要個性化的解決方案。「令人難以置信的是，政策制定者的詞彙量如此有限，甚至無法就此進行明智的對話」，奧馬爾說。 O’Brien 強調了「持續傾聽」的重要性，以了解破壞特定國家、城市或地區覆蓋面的因素。在許多情況下，這意味著與能夠有效解決社區關切的當地領導人進行有針對性的合作。

這種超本地過程也可以擴大規模，許多研究人員正在研究基於證據的工具，可以指導家庭做出明智的疫苗接種決定。 Salmon 和他的同事開發了一個名為 Let’s Talk COVID Vaccines 的線上工具，該工具可根據每個用戶的顧慮提供量身定制的信息。一個更廣泛地鼓勵免疫接種的平台，稱為「讓我們談論預防接種」 (Let’s Talk Shots)，預計將在數週內推出。 Omer 的團隊還制定了一項培訓策略，以幫助醫護人員根據類似的有針對性的信息傳遞原則加強 COVID-19 疫苗的接種，他說，聯合國兒童基金會 (UNICEF) 現在正在調整該團隊的方法以供國際使用。「這不僅僅是直覺——這些是從動機訪談中衍生出來的特定技術，以及從關於如何糾正錯誤信息的實驗中衍生出來的」，他說。

更好的數據對於幫助醫療保健社區快速確定需要介入的地方以防止免疫水平下降過低也至關重要。 O’Brien 說，WHO 一直在與成員國合作，採用該機構的地區衛生信息系統，稱為 DHIS2，這使得共享有關疫苗管理和覆蓋範圍的詳細國內信息變得更加容易。但她也指出，真正的挑戰將是抓住「零劑量」兒童，他們中的大多數生活在住房和基本服務不足的定居點、農村和衝突地區，生活在貧困線以下。「他們出生在設施外，他們從未接種過一次疫苗，他們有點不計其數」，她說。「真的很難計畫出去給你甚至不知道存在的孩子接種疫苗」。2030 年免疫議程的目標之一是將零劑量兒童的數量減少一半，據世界衛生組織估計，這可以在未來 10 年內挽救多達 5,000 萬人的生命。

現在可能是一個獨特的行動機會。公共衛生界對 COVID-19 的應對措施（包括對旅行和公共集會的限制）極大地限制了許多原本會猖獗的傳染病的傳播。儘管發生了辛巴威麻疹疫情等危機，但杜爾海姆說：「我們在許多國家/地區的麻疹病例數達到了我們見過的最低水平」。但隨著越來越多的國家決定——無論明智與否——將大流行病拋在腦後，這一使命的緊迫性只會加劇。 Durrheim 說：「我們要麼現在就必須真正投資並縮小這些免疫缺口，要麼接下來的事情將是毀滅性的」。

自然 612，S44-S46（2022 年）；doi: https://doi.org/10.1038/d41586-022-04341-9

本文是《自然展望：兒童健康》的一部分，關於這個內容是一份在第三方資助下製作的獨立編輯增刊。。

參考文獻：

1.1. Causey, K. et al. Lancet 398, 522–534 (2021).

2.Ho, L. L. et al. Int. J. Infect. Dis. 119, 201–209 (2022).

3.Li, M. et al. Vaccines 10, 1316 (2022).

4.Szilagyi, P. G. et al. Pediatrics 148, e2021052335 (2021).

5.Stoeckel, F., Carter, C., Lyons, B. A. & Reifler, J. Eur. J. Public Health 32, 636–642 (2022).

Vaccination rates are falling, and its not just the COVID-19 vaccine that people are refusing

Society’s best defence against childhood diseases is waning. What needs to be done to help it recover?

Michael Eisenstein/OUTLOOK/19 December 2022/Nature

Credit: Oli Winward

Vaccines offer a potent armour against infectious diseases that once carried a heavy toll of mortality and morbidity, particularly among children. Gaps were already forming in that armour in the years before the COVID-19 pandemic. But amid stagnating vaccination rates, the pandemic acted like a shotgun, punching many more holes in humanity’s defences against preventable diseases such as measles.

Part of Nature Outlook: Children‘s health

The risks of allowing these infections to flourish are clear. Zimbabwe is currently working to contain a huge measles outbreak that claimed the lives of more than 750 children between April and October. And poliovirus has recently re-emerged in the United States after decades of successful elimination, prompting a state of emergency in New York.

The drop in vaccination rates is partly a direct consequence of the pandemic itself, which caused severe interruptions in public-health services and diverted resources. But it isn’t simply a crisis of access to vaccines. The failures and inequities in the global public-health response, coupled with politicization of the pandemic, have also undermined confidence in the institutions and people that coordinate and conduct immunization efforts.

As a result, global vaccination rates have hit their lowest point since 2008 — and getting back on track could be difficult. “We’re talking about tens of millions of lives that are at stake,” says Kate O’Brien, who heads the immunization programme at the World Health Organization (WHO) in Geneva, Switzerland. Rebuilding the trust lost during the pandemic will be a crucial step in pushing back against the global spread of otherwise preventable diseases.

Momentum derailed

For much of the twenty-first century, vaccination efforts were moving in the right direction, continuing a trend that began in the 1970s. In 1974, the WHO initiated its Expanded Programme on Immunization, with the mission of ensuring worldwide access to vaccines against six deadly infectious diseases, including measles. By 2014, global vaccine coverage overall had reached 85% for many vaccine-preventable diseases, and some regions of the world had achieved remarkable successes. The Americas, says O’Brien, had eliminated polio, measles and rubella by 2015, even though those diseases continued to circulate elsewhere.

But vaccination is a continuous process, not a one-time victory, and further progress proved a challenge (see ‘Lost progress’). Jonathan Mosser, an epidemiologist at the Institute for Health Metrics and Evaluation at the University of Washington in Seattle, says that in the years leading up to the pandemic, “we really saw a stagnation of coverage for many of these long-established vaccines”. Furthermore, regional- or national-level statistics can mask considerable inequality at the local level. Duduzile Ndwandwe, a vaccinologist at the South African Medical Research Council in Cape Town points out that although the pre-pandemic coverage for routine childhood vaccines in South Africa was on the order of 85%, there were wide disparities within the country. “The poorest provinces like Eastern Cape, Limpopo and Mpumalanga were not doing that well,” Ndwandwe says. “They would be bordering on 60–70%.” This is well short of the 90% or more that is generally considered necessary for robust control of vaccine-preventable diseases.

Source: The World Bank

By 2019, measles outbreaks were popping up with alarming frequency and posing a real global threat. “The scale of those outbreaks in 2019 was colossal, and we saw large increases in the number of deaths,” says David Durrheim, who studies public health at the University of Newcastle in Australia. “We saw countries being overwhelmed.” That year saw more than 200,000 measles deaths worldwide, a 50% increase over the 2016 total. There were a number of reasons for this backslide, including inadequate resources for vaccination programmes and the low priority given to immunization efforts in some countries. But rising vaccine hesitancy throughout the world was also an important factor, and the WHO named this trend one of the ten greatest threats to global health in 2019.

This perilous situation motivated the WHO to develop its Immunization Agenda 2030, which was announced in April 2020 with the goal of achieving 90% global coverage for the standard battery of childhood vaccines while also accelerating the introduction of new immunizations to low-income countries.

Delayed doses

But this announcement came mere weeks after the organization formally declared COVID-19 to be a pandemic. “It shut things down,” says O’Brien. “Compared with how many doses were given in the same month of the previous year, you just see this absolute plummeting in April, May and June of 2020.”

Routine paediatric vaccinations took a serious hit throughout the first year of the pandemic. Mosser and his colleagues combed through data from sources such as the WHO, and estimated that in 2020, COVID-19 led to 8 million to 9 million missed doses of routine childhood vaccines for diseases such as measles, rubella and diphtheria1. Some parts of Africa and Asia saw by far the sharpest drop in rates, but high-income countries in other regions also experienced dips at the start of the pandemic.

Much of this early impact was directly attributable to the strong measures taken to contain the spread of the SARS-CoV-2 virus, with many jurisdictions limiting travel, closing schools and restricting access to non-urgent medical care. But health-care providers were also struggling with limited capacity. “Resources and expertise were diverted from many sectors of health care, including immunization systems, to COVID response,” says Mosser. Even when there were no formal impediments to scheduling a visit to a health-care provider, social and psychological factors came into play that further undermined timely vaccination. “COVID kind of created the fear of even being in contact with the health-care services,” says Ndwandwe.

The pandemic also brought many targeted vaccination campaigns for children in resource-limited settings to a grinding halt. An analysis by the WHO found that by May 2020, nearly 60% of the 183 vaccination campaigns scheduled were either cancelled or delayed2.

As the immediate shock of COVID-19 passed, routine childhood vaccination efforts began to pick up steam again — particularly in higher-income countries. But even in wealthy regions, the pandemic amplified structural inequalities in the health-care system, and has left many underserved communities less protected against vaccine-preventable diseases. For example, Durrheim says that “in New Zealand, the second-dose coverage for measles has dropped to just above 80%, and that has fallen disproportionately in Māori, First Nations people and Pacific Islanders”.

In lower-income countries, the rebound has been more uneven. By the end of 2021, 16% of the vaccination campaigns scheduled by the WHO pre-pandemic had been cancelled or were still suspended, resulting in 382 million missed doses worldwide. O’Brien also notes that — somewhat paradoxically — the intense focus of the health-care community on delivering immunizations against COVID-19 sometimes meant the standard array of childhood vaccines were put on the back burner in favour of achieving pandemic control. “That’s why in 2021, we didn’t see the recovery that we thought was going to happen,” she says. Nevertheless, several countries, including Nepal, Bangladesh, Thailand and Pakistan, have been able to hold steady and maintain high coverage over the past three years by continuing to prioritize routine childhood immunization despite limited resources.

Confidence lost

But efforts to regain lost ground in vaccine coverage are also being jeopardized by other legacies of the pandemic, including the erosion of trust in governments and public-health institutions — a trend that the advent of COVID-19 vaccines has exacerbated rather than dampened.

Long before COVID-19 vaccines were even available for children, they had become a flash point for controversy — most notably, but not exclusively, in the United States. Daniel Salmon, a vaccinologist at Johns Hopkins University in Baltimore, Maryland, thinks some of the problems people have with the vaccine go back to its origins in Operation Warp Speed. This multi-billion-dollar US public–private partnership aimed to develop pandemic vaccines within an unprecedented, time frame. In particular, he is critical of the programme’s emphasis on speed without parallel planning around building public acceptance. “You’ve got to get people to want the vaccine,” says Salmon. “That wasn’t their goal.”

A worker with the Expanded Programme on Immunization prepares a measles vaccine at a health clinic in Nowshera, Pakistan.Credit: WHO/Asad Zaidi

Against the already politicized backdrop of the US COVID-19 response, the failure to generate public trust and enthusiasm around COVID-19 vaccines — particularly those developed with the relatively new messenger-RNA-based technologies — has created problems that will be difficult to solve. “Many people initially thought that by going on CNN and furrowing our brows, we would convince people to get vaccinated,” says Saad Omer, director of the Yale Institute for Global Health in New Haven, Connecticut, referring to the US news channel. “That’s not how vaccine persuasion works.” And when adults lack confidence in the vaccine, the likelihood of them immunizing their children plummets. As of October 2022, only 37% of eligible children in the United States had received even a single dose.

Although before the pandemic most US parents took their children to be vaccinated against multiple diseases to comply with school mandates, Salmon estimates that between one-third and one-quarter had serious concerns about the safety and necessity of these routine childhood vaccinations. “It’s the fence-sitters, the people who could be pushed over the edge, that worry me,” he says. This issue has become more salient in the context of COVID-19. For example, several reports have described cases of inflammation of the heart tissue — a condition called myocarditis — among adolescent boys receiving multiple shots of the mRNA vaccines3.

Although these cases are rare, mild and tend to resolve on their own, such safety concerns might shift the likelihood of vaccinating among parents who were already wavering. Framing these side effects relative to the much greater threat posed by COVID-19 itself is a challenge for governments and public-health organizations. “Public-health people need to be transparent,” says Katie Attwell, who studies vaccination policy at the University of Western Australia in Perth. “They do need to talk about the risks, and they need to contextualize the risks.”

The extent to which concerns about COVID-19 shots are fuelling hesitancy around other vaccines remains unclear. But some who study vaccine uptake are already concerned. “It’s going to take time to get data, but I would not be surprised if we see substantial drops in routine vaccines — especially in populations that have really been refusing COVID vaccines,” says Salmon. Omer’s research is already picking up some early indications of reduced uptake for the tetanus, diphtheria and pertussis vaccine among people in the United States who are pregnant. And even though these are still preliminary findings, he says “my concern is that this is sort of an iceberg where we’re just beginning to see the tip”.

There is also a clear political component to vaccine perception in the Western world. A 2021 survey4 of 1,745 US parents found that those who vote Republican are more than twice as likely to forego vaccinating their children against COVID-19 than parents affiliated with the Democratic party. For some people, at least, vaccine acceptance is deeply intertwined with political identity. An analysis5 of vaccine confidence in Europe found that vaccine hesitancy and refusal are closely tied with right-wing, populist politics.

And the possibility remains that this mistrust will spread globally. Heidi Larson, an anthropologist at the London School of Hygiene and Tropical Medicine, says “there is clearly a globally coordinated, very deep, negative network out there” exploiting pandemic-era mistrust to propagate and promote a broader anti-vaccine agenda through social networks such as Twitter and Facebook. In South Africa, Ndwandwe sees such vaccine hesitancy propagating mainly in more affluent communities that have the time and resources to find information — and misinformation — on the Internet. “TikTok is one of the more dangerous platforms that I have seen,” she says. “That’s where a lot of these things are happening.” In poorer communities without easy Internet access, the conversation is just as readily driven by radio broadcasts, religious leaders or poster campaigns, Omer says.

Overcoming hesitation

It would be a mistake, however, to simply attribute vaccine hesitancy to fear or misunderstanding of the science. As director of the Vaccine Confidence Project, a non-profit initiative based at the London School of Hygiene and Tropical Medicine focused on tracking global public sentiment around immunizations, Larson has been able to tease out some of the motives underlying the decision to vaccinate or not. According to her preliminary assessment of recent unpublished data from Africa and the European Union, many people are hesitant simply because they don’t see the importance of being vaccinated for diseases that they do not see as a real concern.

This is in keeping with Ndwandwe’s experience in South Africa. She says that mothers who already routinely engage with medical systems often trust their physician’s or nurse’s guidance that an immunization is important, even at the height of a pandemic. But the story is different in poorer communities, where people often need to make considerable trade-offs when seeking even routine care. “You’re talking about competing priorities here,” she says. “Do I want to travel 10 kilometres to go and sit in a clinic for the whole day, instead of going to a job that will pay me money and actually feed my kids?”