Can the COVID Vaccine Cause High Blood Pressure?

COVID-19 vaccines can temporarily raise blood pressure in a small percentage of recipients. A systematic review and meta-analysis pooling data from over 357,000 people found that roughly 3% experienced abnormal or increased blood pressure after vaccination, while severe spikes qualifying as hypertensive urgencies or emergencies occurred in a much smaller fraction. For most people, the increase is mild and short-lived, but the phenomenon is real enough that researchers have called it “not rare” and recommended that clinicians pay attention to it, especially in people who already have high blood pressure.

How Common Are Blood Pressure Changes After Vaccination

The most comprehensive look at the numbers comes from a 2022 meta-analysis published in the Journal of Cardiovascular Development and Disease. Across the included studies, 357,387 subjects were tracked, with 13,444 events of abnormal or increased blood pressure recorded. After the researchers excluded statistical outlier studies, the pooled estimated proportion of abnormal or increased blood pressure after vaccination came to about 3.2%. Cases of stage III hypertension or hypertensive urgencies and emergencies were far less common, estimated at around 0.6%.¹

To put that in perspective, roughly 97 out of 100 people in these studies showed no significant blood pressure change. Of the roughly 3 who did see a rise, only a small subset experienced anything clinically dangerous. That said, when you multiply a 3% rate by hundreds of millions of vaccine doses administered worldwide, even a small percentage translates to a noticeable number of people who felt something unusual and may have wondered whether their vaccine was responsible.

What Happens in the Body

Researchers have proposed several mechanisms to explain why blood pressure might tick upward after a COVID-19 shot. The leading hypothesis involves the spike protein that the vaccines instruct your cells to produce. This spike protein interacts with ACE2 receptors on the surface of cells. ACE2 plays a key role in regulating blood pressure by breaking down a hormone called angiotensin II, which constricts blood vessels. When the vaccine-generated spike proteins temporarily occupy ACE2 receptors, they may reduce ACE2’s ability to clear angiotensin II, allowing that vessel-constricting signal to build up. Researchers have described this as the “Spike effect,” noting that it mirrors some of the cardiovascular features seen during actual COVID-19 infection.²

There is also an immune-system dimension. Any vaccination triggers an inflammatory response; that is how it trains your immune system. The burst of cytokines and other inflammatory molecules released in the hours after a shot can temporarily affect blood vessel tone, potentially nudging blood pressure upward. A Greek study measuring endothelial function (how well blood vessels relax and contract) found that after the second dose of an mRNA vaccine, there was a transient deterioration in endothelial function. The change reversed within 48 hours, leading the researchers to conclude it represented “nonsignificant harm.”³

A third factor that researchers have raised is psychological stress. Anxiety about needles, worry about side effects, or even the clinical environment itself can trigger a “white coat” blood pressure rise. Separating this anxiety-driven spike from a genuinely physiological one is difficult in studies that measure blood pressure only at the vaccination site. Some of the 3.2% who registered elevated readings may have had stress-related spikes that would have happened with any injection.

Timing, Dose Number, and How Long It Lasts

Blood pressure changes after vaccination tend to show up within the first day or two and resolve relatively quickly. The endothelial function study mentioned above saw changes revert to normal by the 48-hour mark. Case reports and survey data generally align with this pattern: people notice a higher-than-usual reading the day of or the day after their shot, and things settle within a few days.

The dose number appears to matter. A survey of institutional workers who received mRNA vaccines found that blood pressure alterations presented with greater frequency at the second or booster dose compared to the first.⁴ The Greek endothelial study observed no meaningful changes after the first dose but detected changes after the second, reinforcing the idea that repeated immune activation may contribute.³ If you sailed through your first dose with no blood pressure issues but felt something different after the second, that pattern tracks with the published data.

Most of the evidence points to this being a transient phenomenon. There is limited data suggesting that vaccines cause lasting, permanent increases in blood pressure. The meta-analysis authors noted that the basic mechanisms require further research, but the clinical picture from the studies available is one of short-lived spikes, not new-onset chronic hypertension.

Who Might Be More Susceptible

People who already have high blood pressure or are on blood pressure medication appear to be the group most likely to notice a change. If your baseline is already elevated, a small additional push from an immune response can cross into a range that feels symptomatic or shows up as an alarming reading on a home monitor. This is one reason some researchers have recommended that hypertensive patients monitor their blood pressure in the days following vaccination.

Interestingly, the ACE2 mechanism research suggests that age and health status may influence vulnerability in a counterintuitive way. One paper found that increased activity of enzymes that compensate for ACE2 (called POP and PRCP) is typical in elderly individuals with existing cardiovascular issues, but not in younger, healthier people. The implication is that adverse reactions linked to angiotensin II buildup could actually be more common in younger, healthier subjects whose compensatory enzyme systems are less active.² This does not mean younger people face greater overall risk from vaccination, but it may help explain why some otherwise-healthy younger adults reported unexpectedly elevated blood pressure after their shots.

Gender differences have appeared in surveillance data, though the evidence is not strong enough to draw firm conclusions about who faces higher risk by sex. Similarly, the specific vaccine platform (mRNA versus viral vector) has been discussed in the literature, but the available data does not yet clearly separate risk by vaccine type.

Surveillance Data and What It Can and Cannot Tell You

Some of the attention around this topic has come from passive surveillance systems like the Vaccine Adverse Event Reporting System (VAERS) in the United States. A retrospective study using VAERS data identified 33,754 cases of cardiovascular events associated with COVID-19 vaccines, spanning different age groups and both sexes. Statistical measures suggested a significant association between cardiovascular events and the vaccines.⁵

VAERS numbers need careful interpretation, though. The system is designed to catch safety signals early, not to prove that a vaccine caused a particular event. Anyone can file a report, and reports are not verified for accuracy or causation before being logged. During the COVID-19 vaccination campaign, public awareness of VAERS was unusually high, which increases the likelihood that events were reported more frequently than they would have been for other vaccines. A VAERS signal says “this is worth investigating,” not “this was caused by the vaccine.” The meta-analysis data, which comes from controlled studies rather than voluntary reporting, provides a more reliable estimate of the actual rate.

That said, the VAERS data and the meta-analysis point in the same direction: blood pressure changes after COVID-19 vaccination are a real phenomenon, not a reporting artifact. The question is how often they happen and how much they matter clinically, and the controlled studies suggest the answer is “sometimes” and “usually not much.”

Pregnancy and Hypertensive Disorders

One population that has received special attention is pregnant women, because high blood pressure during pregnancy can lead to serious complications like preeclampsia. A study comparing women who were vaccinated during or just before pregnancy to unvaccinated women found a slightly elevated risk of hypertensive disorders of pregnancy, with an adjusted relative risk of 1.24. However, the researchers explicitly cautioned that the vaccinated and unvaccinated groups came from different survey cohorts with different characteristics, making it impossible to conclude that the vaccine caused the difference.⁶

This is a good example of how observational data can generate concern without providing a clear answer. Women who chose to be vaccinated during the pandemic may have differed from those who did not in ways that affect pregnancy outcomes, such as healthcare access, underlying health conditions, or employment in essential jobs with higher exposure risk. The study authors called for updated assessments of hypertensive disorder risk after both COVID-19 illness and vaccination, acknowledging that the current data is not sufficient to draw causal conclusions.

Major health organizations have continued to recommend COVID-19 vaccination for pregnant individuals, weighing the documented risks of COVID-19 infection during pregnancy (which include preeclampsia, preterm birth, and stillbirth) against the relatively modest and uncertain signal around blood pressure changes from the vaccine itself.

How This Compares to COVID-19 Infection Itself

Any conversation about vaccine side effects is incomplete without considering what happens when someone catches the virus instead. COVID-19 itself is well-documented to cause cardiovascular complications, including sustained high blood pressure. The virus uses the same ACE2 receptors that the vaccine’s spike protein interacts with, but a live infection produces far more spike protein over a longer period, and adds direct viral damage to blood vessel linings, severe systemic inflammation, and potential blood clotting issues on top of the ACE2 disruption.

Studies of “long COVID” have found that blood pressure problems can persist for months after infection in some people. The transient, generally mild blood pressure bump from vaccination looks quite different from this picture. The vaccine produces a controlled, limited amount of spike protein that the body clears within days, whereas an active infection is an uncontrolled process that can last weeks and cause damage across multiple organ systems.

This does not mean vaccine-related blood pressure changes should be dismissed. For someone whose blood pressure is already poorly controlled, even a short-lived spike could theoretically trigger a cardiac event. But on a population level, the cardiovascular risk from unvaccinated exposure to COVID-19 substantially exceeds the cardiovascular risk from the vaccine.

What to Do If Your Blood Pressure Rises After a Shot

If you check your blood pressure in the days after vaccination and notice it is higher than usual, the first step is not to panic. A rise of 10 to 20 points in systolic pressure is within the range of what these studies have observed, and it typically resolves on its own. Here are some practical considerations:

• Keep measuring: Check your blood pressure a few times a day for two or three days. A single elevated reading does not tell you much. A pattern of readings that stay high beyond three to four days is worth mentioning to your doctor.
• Stay on your medications: If you already take blood pressure medication, do not adjust your dose on your own because of a post-vaccine spike. Your existing regimen should help buffer the rise.
• Watch for warning signs: Severe headache, chest pain, blurred vision, or shortness of breath alongside very high readings (above 180/120) warrant urgent medical attention regardless of whether you recently had a vaccine.
• Context matters: Pain from the injection site, poor sleep, and stress about side effects can all independently raise blood pressure. If you are sore and anxious, your reading may be elevated for reasons that have nothing to do with the vaccine’s biological effect on your blood vessels.

For people with well-controlled hypertension, there is generally no reason to avoid vaccination. The transient nature of the blood pressure changes, combined with the cardiovascular risks of COVID-19 infection, means that vaccination remains the lower-risk option. Some clinicians have suggested that hypertensive patients measure their blood pressure before the vaccination appointment to establish a baseline, making it easier to assess any post-vaccine change in context.

The Stress and Anxiety Factor

It is worth spending a moment on how much of the reported blood pressure increase might stem from the vaccination experience rather than from the vaccine itself. Blood pressure is exquisitely sensitive to emotional state. Sitting in a chair at a pharmacy or clinic, watching the needle approach, and then spending the observation period wondering whether you are about to have a reaction is a recipe for a stress-related blood pressure spike in anyone, but especially in people who are anxious about medical procedures.

Researchers have noted the difficulty of disentangling this psychological component from true pharmacological effects. In clinical trials for other medications, the “nocebo effect” (experiencing negative symptoms because you expect them) is well-documented and can account for a surprising proportion of reported side effects. During the COVID-19 vaccine rollout, extensive media coverage of potential adverse events likely primed many recipients to be hypervigilant about any change they felt in their body, including the pounding heartbeat and flushed face that accompany anxiety and are easy to interpret as high blood pressure.

None of this means that every reported blood pressure increase was “all in someone’s head.” The biological mechanisms discussed earlier are plausible and supported by objective measurements of endothelial function. But the stress contribution is probably non-trivial, and it is one reason that home blood pressure readings taken in the calm of your own living room a day or two after vaccination may give a more accurate picture than a reading taken at the vaccination site immediately after the shot.

Why the Research Is Still Evolving

The meta-analysis authors themselves noted that the basic mechanisms behind post-vaccination blood pressure changes “are still unclear and require further research.”¹ Several gaps remain. Most studies measured blood pressure only in the immediate aftermath of vaccination, so the time course beyond a week is poorly mapped. The meta-analysis pooled data from studies with very different designs, some measuring blood pressure at the vaccination clinic and others relying on self-reported home monitoring, which introduces variability. And few studies were designed specifically to answer the blood pressure question; many were reporting it as a secondary finding alongside broader safety surveillance.

The wide confidence intervals in the meta-analysis tell a similar story. The pooled proportion of abnormal blood pressure was estimated at 3.2%, but the 95% confidence interval ranged from about 1.6% to 6.2%, meaning the true rate could plausibly be half or double the central estimate.¹ For stage III hypertension, the confidence interval was even wider, from 0.1% to 5.1%. These are not narrow, precise estimates; they are early attempts to quantify something that had not been systematically tracked before the pandemic.

As updated vaccines continue to be developed for new variants, ongoing monitoring of cardiovascular effects will remain important. Whether newer formulations carry the same blood pressure signal, or whether reformulated vaccines targeting different spike protein configurations alter the ACE2 interaction, are open questions that researchers will need to address with each new generation of shots.