The story: why vaccine uptake remains low
COVID-19, influenza (flu), and respiratory syncytial virus (RSV) cause millions of illnesses in the United States each year, leading to thousands of hospitalizations and deaths.
Despite evidence that immunization reduces the risk of severe illness, hospitalization, and death, uptake remains low across all three diseases. During the 2025–2026 season, fewer than half of adults received a flu vaccine, and only 17.5 percent received a COVID-19 vaccine. RSV protection among eligible infants was higher, with 65.1 percent protected through either maternal vaccination or preventive antibody immunization. Among adults, RSV vaccine uptake reached 43.2 percent for those ages 75 and older and 32.8 percent for adults ages 50–74 with a high-risk condition.
What drove online conversation about flu, COVID-19, and RSV in California?
The three respiratory viruses generated different conversation patterns throughout the year. Select the buttons below to explore the patterns for each virus.
Flu conversation followed a seasonal pattern, with peaks driven by local disease severity and changes to federal guidance
Conversation about flu vaccines followed a clear seasonal pattern that closely aligned with the respiratory virus season. Discussion was elevated from January through mid-March, declining during the summer months, and began increasing again in August.
Overall conversation volume throughout the year (132,000 mentions) was substantially lower than for COVID-19 vaccines, but higher than for RSV immunizations.
Peaks in conversation were driven primarily by California-specific events, including seasonal vaccination campaigns, regional public health recommendations, and reports of local flu cases and deaths. The trendline below highlights the primary drivers of these increases.
COVID-19 conversation was driven by national vaccine policy, access, and safety concerns throughout the year
Conversation about COVID-19 vaccines was relatively high throughout the year. Discussion was elevated from January through March, with spikes continuing through the summer and into the fall and winter.
Overall conversation volume throughout the year (756,400 mentions) was the highest of the three immunizations.
Unlike flu and RSV, discussion was driven less by seasonal virus activity than by national developments, including changes to federal vaccine policy and access, state responses to those changes, and viral claims about vaccine safety. The trendline below highlights the events that drove these increases in conversation.
RSV conversation was driven by seasonal immunization promotion, sparking comparatively little discourse on its own
Like flu, conversation about RSV immunizations—including both vaccines and monoclonal antibodies—followed a clear seasonal pattern, increasing during the winter months through March, declining over the summer, and rising again beginning in August.
Overall conversation volume throughout the year (31,700 mentions) was substantially lower than for flu and COVID-19.
Peaks in conversation were driven primarily by California-specific immunization campaigns and other state and local communications about RSV prevention. The trendline below highlights the events that drove these increases in conversation.
Online mentions of flu, COVID-19, and RSV immunizations in 2025
Select a number on the trendline to see what drove conversation.
Scroll the chart sideways to see the full year.
Flu vaccines: conversation peaks
COVID-19 vaccines: conversation peaks
RSV immunizations: conversation peaks
| Month | Flu | COVID-19 | RSV |
|---|
Source: Infodemiology.com analysis, 2026. Note: Weekly online mentions of flu, COVID-19, or RSV in California during 2025 include social and digital media, online video platforms, news sites, blogs, forums, Q&A sites, and other web-based sources. Several posts mention more than one vaccine and are counted once for each vaccine they reference. All three viruses share one vertical scale so volumes can be compared directly; because COVID-19 conversation was roughly six times the volume of flu conversation, the flu and RSV lines sit low on the axis.
How does the public perceive each vaccine?
Underlying concerns and beliefs about each vaccine differed. Flu conversations centered on vaccine efficacy, with questions about whether the vaccine actually worked. COVID-19 conversations were dominated by safety doubts and institutional distrust. RSV generated lower overall discussion but also showed strong public recognition that the disease poses a serious risk to infants and older adults. Select the buttons below to learn more about public perceptions.
Concerns about effectiveness were driven by anecdotes about illness after vaccination and low perceived risk
Flu vaccine conversation was dominated by concerns about effectiveness. Many people appeared to judge the flu vaccine by whether it prevents infection, with limited recognition that its primary benefit is reducing severe illness, hospitalization, and death. Closely tied to these discussions was the persistent misconception that the flu vaccine causes the flu.
Perceptions that the vaccine offers limited value—or can make people sick—were driven by anecdotal accounts of illness following vaccination, widespread misinterpretation of a study on vaccine efficacy, concerns about vaccine strain mismatches, and the false belief that the inactivated virus used in the vaccine can cause infection. These narratives often coincided with a preference for natural immunity or alternative prevention measures, supported by low perceived risk from influenza, skepticism about media coverage of flu cases and deaths, and low confidence in vaccine effectiveness.
Safety concerns extended beyond flu-specific claims
Safety and ingredient concerns were also common. Some questioned vaccine ingredients or raised concerns about side effects. While many of these narratives focused on flu-specific claims—such as concerns about Guillain-Barré syndrome or allegations that the vaccine contains harmful ingredients like mercury—others borrowed claims more commonly associated with COVID-19 vaccines, including myocarditis and cancer. These cross-vaccine narratives were most common when flu and COVID-19 vaccines were promoted together, but also appeared in discussions of flu vaccination alone.
Recognition of disease severity and protecting vulnerable groups drove support
Supportive flu vaccine narratives were often grounded in firsthand experience with the flu and recognition of its potential severity. People described prolonged illness or serious complications, and many emphasized protecting vulnerable groups, including young children, older adults, and those with chronic illnesses. These discussions suggest that messaging focused on disease severity and protection of others may be more persuasive than messaging centered on personal risk reduction.
Safety concerns and institutional distrust shaped discussion
COVID-19 vaccine conversation was dominated by negative perceptions, misconceptions, and false narratives. The most common themes centered on vaccine safety and side effects, followed by doubts about effectiveness and beliefs that COVID-19 no longer poses a serious health risk, particularly for children.
Broader anti-vaccine narratives were also common. Many expressed a preference for natural immunity, supported policy changes that limited vaccine access, or criticized past and current infection prevention measures. Distrust of federal health agencies, the media, public officials, pharmaceutical companies, and state and local health departments was a defining feature of these discussions.
Changes to federal recommendations created confusion about access
Although supportive voices represented a minority of the conversation, they frequently expressed frustration with changing federal recommendations, confusion about vaccine eligibility and insurance coverage, and fatigue with persistent opposition to COVID-19 vaccination. Conflicting federal and state guidance prompted many people to seek clarification about eligibility and access, while others shared their own vaccination experiences to answer questions or reassure others.
Experience with mild illness carried more weight than statistics on severity, making messaging feel disconnected
Personal experience shaped perspectives across both supportive and opposing narratives. Many used their own experiences with COVID-19 infection or vaccination to justify their views, often concluding that their personal risk of severe illness was low. This highlights a disconnect between public health messaging focused on preventing severe illness and hospitalization and many people’s lived experience.
Supportive commenters most often emphasized protecting people at highest risk and reducing the likelihood of long COVID, suggesting these themes may resonate more than appeals focused solely on personal risk or short-term illness.
Disease severity was widely recognized, particularly for infants and older adults
Unlike flu and COVID-19, RSV was widely recognized as a serious illness, particularly among populations eligible for immunization. Personal experience was central to these discussions. Parents shared stories of infants becoming seriously ill with RSV and expressed appreciation for being able to protect them through immunization, while older adults described RSV as more debilitating than they had expected. This contrasted with conversations about flu and COVID-19, where recognition of disease severity was less common.
Amid changes to federal immunization recommendations, many questioned the decision to move RSV immunization to shared clinical decision-making. Given the perceived severity of RSV—particularly for young children—these commenters expressed strong support for maintaining broad access to immunization. This broader recognition of risk for vulnerable populations suggests that messaging emphasizing protection against serious illness may resonate, particularly among parents and older adults.
Fears about equity and access reflected concerns about who could benefit
Conversations about RSV also differed from flu and COVID-19 in their focus on equity and access. Even among people who were not eligible for RSV immunization, many acknowledged the virus’s potential severity, with some calling for eligibility to be expanded to younger adults and other groups not currently recommended for vaccination.
Some expressed frustration with age cutoffs or risk-based criteria, while others welcomed expanded eligibility for adults ages 50–74 with risk factors, emphasizing reduced barriers and easier access compared with prior requirements. These conversations suggest that even when disease severity is recognized, confusion persists about who qualifies for vaccination and why recommendations are limited to certain populations.
Safety concerns reflected the higher stakes of immunization decisions for vulnerable populations
Unlike flu and COVID-19 discussions, RSV conversations focused less on questions of effectiveness and more on safety in specific populations. Some concerns centered on legitimate safety signals identified in older adults, including FDA warnings about Guillain-Barré syndrome. Others alleged that RSV vaccination during pregnancy was linked to preterm birth or argued that the immunization had been approved without adequate evidence of long-term safety, particularly for older adults.
How California’s respiratory virus messaging aligned—and conflicted—with public conversation
Comparing official messaging with public conversation highlights where messaging aligned with public concerns and where important gaps remained. Select a finding to see detailed insights and what they mean.
Bundling vaccines may simplify communication, but can also blur how people interpret each vaccine
Messaging about respiratory viruses from health entities and government pages focused most on flu vaccines, often promoting the vaccine on its own (46 percent of posts). However, communications also frequently promoted COVID-19 vaccines alongside flu vaccines (21 percent), or promoted flu, COVID-19, and RSV immunizations together (19 percent). The chart below shows the types of vaccines discussed in health entity messages.
Rarely did messaging promote RSV or COVID-19 immunizations on their own (7 percent and 3 percent, respectively). Most messaging that promoted RSV immunization also promoted both flu and COVID-19 vaccines.
While bundling respiratory virus immunizations reflects common public health communication practices, our analysis suggests it can blur important differences in how people perceive each immunization.
As shown throughout this report, promoting vaccines together can also allow concerns about one vaccine to spill over into conversations about the others.
Vaccines discussed in health entity messaging
Share of messaging by the vaccine or vaccines promoted.
Source: Infodemiology.com analysis, 2026. Note: Analysis of health entity and government page messaging is limited to Facebook.
People based vaccine decisions on perceived risk and continued to seek basic information elsewhere online
Health and government communications generally relied on five messaging approaches:
- Prevention: Framed immunization as one part of preventing severe illness alongside masking, hand hygiene, and staying home when sick.
- Seasonal risk: Highlighted seasonal increases in respiratory viruses and the importance of timely vaccination.
- Guidance and eligibility: Shared current recommendations, eligibility criteria, and schedule updates.
- Access: Promoted free clinics, mobile vaccination events, insurance coverage, MyTurn.CA.gov, and walk-in appointments.
- Bundled immunizations: Encouraged receiving multiple respiratory virus immunizations during the same visit.
Although these messages aligned with public health guidance, they did not always align with how people interpreted respiratory virus risk. Messaging frequently emphasized preventing severe illness during seasonal surges, while many commenters judged the need for vaccination based on their own experiences with the virus. For people who viewed their personal risk as low, messages focused on disease severity were often unpersuasive.
Health agencies routinely clarified eligibility, recommendations, and where vaccines were available. Despite these efforts, many people continued to ask basic questions elsewhere online, suggesting that this information was not consistently reaching the audiences who needed it or was being overshadowed by broader online conversations.
Engagement metrics provided important additional context
Public comments did not fully reflect overall engagement with health messaging. Although comment sections often appeared overwhelmingly opposed to vaccination, reactions told a different story.
Across analyzed posts, approximately 65 percent of reactions were likes or loves, compared with 29 percent laughing reactions and 5 percent angry reactions.
Engagement varied considerably by both messenger and content. Posts from health systems received overwhelmingly positive reactions, while state agency posts attracted substantially more mocking responses than similar content shared by county health departments. Standalone posts about individual vaccines also received more positive engagement than posts promoting multiple respiratory virus immunizations together, particularly those combining flu and COVID-19 vaccination. The charts below show the reaction type by author category.
How people reacted to vaccine messaging
Share of reactions by the vaccine or vaccines promoted. Compare reactions across different types of health organizations.
Source: Infodemiology.com analysis, 2026. Note: Analysis of health entity and government page messaging is limited to Facebook. Reactions shown as a share of all reactions on each group of posts.
What do the patterns suggest for communicators preparing for respiratory virus season?
As communicators prepare for the 2026–2027 respiratory virus season, this analysis highlights several strategies to strengthen messaging about COVID-19, flu, and RSV immunization. Although this report focuses on California, many of the observed themes mirror national trends and may be relevant to communicators across the United States. Select a takeaway below to view the full recommendation.
Co-administration remains an important strategy for improving uptake, and many respiratory virus immunizations are recommended during the same period. However, increasing standalone communications for each immunization may better address the specific questions, concerns, and motivations associated with each virus while reducing the spillover of hesitancy from one vaccine to another. This is particularly important for RSV, which was often discussed only in the context of flu and COVID-19 rather than on its own.
Confusion about eligibility and access increased following changes to federal recommendations, but many questions extended beyond those policy announcements. Clear, consistent messaging about who is eligible, where immunizations are available, and what current recommendations are—distributed through both owned channels and partners—can help reduce confusion before it spreads.
Trust varies widely across audiences, making messenger selection as important as message content. Health systems, health care professionals, and local health departments remain important sources for many people. At the same time, personal stories from community members can help reach audiences who are skeptical of government institutions or traditional public health messaging.
Tailor messages to how different audiences experience respiratory viruses. People evaluated the need for vaccination through the lens of their own experiences and risk, which often differed by virus and stage of life. Messaging that acknowledges those experiences while emphasizing benefits that resonate with specific audiences—such as protecting vulnerable family members, reducing illness severity, or preventing long-term complications—may be more persuasive than messages focused solely on severe outcomes. Because RSV was widely recognized as a serious illness, messages emphasizing protection of infants and older adults may be particularly effective.
Many safety and effectiveness concerns about flu and COVID-19 vaccines appeared to reflect firmly held beliefs rather than genuine information seeking. Communicators should prioritize responding to legitimate questions, particularly in the comment sections of owned content, where clear, evidence-based answers can build trust. Broadly engaging with entrenched narratives may reinforce existing beliefs or draw additional attention to myths without reaching audiences who remain open to vaccination.