Rise In Heart Attack Cases Post Covid-19 Vaccination in India: A Review Article

Abstract

In the aftermath of the global COVID-19 vaccination campaigns, rare but serious adverse events related to thrombosis and clotting disorders (including vaccine-induced immune thrombotic thrombocytopenia, VITT / TTS) have been reported, raising concerns about cardiovascular safety. In India, with widespread use of Covishield (ChAdOx1 nCoV-19 / AZD1222) and Covaxin (BBV152), questions have been posed about a possible rise in heart attacks (acute myocardial infarction, AMI) and coronary thrombosis following vaccination. This review examines the pharmacological plausibility, epidemiological and clinical evidence, and reported statistics of clotting events post COVID-19 vaccines in India, with particular scrutiny of whether a genuine increase in heart attack incidence has occurred, or whether associations are coincidental. We review mechanistic hypotheses (e.g. platelet factor 4 interactions, complement activation, endothelial dysfunction), case series and observational studies from India and internationally, and nationally collected serious adverse event data. In India, serious adverse events following immunization (AEFI) causality assessments up to March 2022 included thromboembolic events in ~18.8% of serious AEFI reports (209/1,112) but found no consistent causal association with particular vaccine types. A single Indian center study of coronary thrombo-embolic events reported 42% of acute coronary syndrome patients had prior vaccination within ~5 months, but did not establish causality. A larger observational study in Delhi (n = 1,578) found no clustering of AMI post-vaccination and actually lower adjusted mortality in vaccinated patients. Overall, the current evidence does not robustly support a rise in vaccine-induced heart attacks in India. The balance of risks remains in favor of vaccination. However, sparse data, underreporting, and methodological limitations impose caution. We conclude with suggestions for better pharmaco-vigilance, prospective studies, and mechanistic research to clarify the residual uncertainty.

Keywords

Introduction

1.1. Background and Rationale

COVID-19 (caused by SARS-CoV-2) remains a major global health burden. Vaccination has been a key strategy to reduce morbidity and mortality. In India, two main vaccines have been deployed:

1. Covishield (the Indian-manufactured version of the Oxford–AstraZeneca adenoviral vector vaccine, ChAdOx1 nCoV-19/AZD1222)
2. Covaxin (BBV152, an inactivated whole-virus vaccine developed by Bharat Biotech in collaboration with Indian Council of Medical Research)

These vaccines were rolled out beginning in early 2021 under emergency use authorization, often concurrently or sequentially.While vaccines are generally safe, rare but serious adverse events (SAEs) have drawn attention. Among these, thrombotic events associated with thrombocytopenia, sometimes termed TTS (thrombosis with thrombocytopenia syndrome) or VITT (vaccine-induced immune thrombotic thrombocytopenia), have been observed especially with certain adenoviral vector vaccines. Because coronary thrombosis is a mechanism of heart attacks (acute myocardial infarction, AMI), a theoretical possibility is that vaccination might, in rare cases, increase the risk of coronary thrombotic events.Public and scientific interest has thus emerged around whether there has been any rise in heart attack cases post COVID-19 vaccination in India, whether temporal clustering exists, and whether causality is plausible. This review aims to synthesize what is known about the pharmacology, mechanisms, case reports, epidemiology, and national surveillance data relevant to this question, and provide a balanced appraisal.

1.2. OBJECTIVES

1. To review the types of COVID-19 vaccines used in India and their known adverse event profiles.
2. To examine mechanistic and pharmacologic pathways by which vaccines might trigger thrombosis or platelet activation relevant to coronary circulation.
3. To survey Indian and international clinical/epidemiological evidence regarding coronary thrombosis or heart attacks associated temporally with COVID-19 vaccination.
4. To analyze national AEFI / pharmacovigilance data in India as pertains to thrombotic and cardiovascular events.
5. To assess whether there is credible evidence for a rise in heart attack incidence attributable to vaccines, discuss limitations, and propose directions for further research.

2. METHODS

A narrative review methodology was used, emphasizing peer-reviewed literature, government reports, and pharmacovigilance data. Searches included PubMed, Google Scholar, national data repositories, and official Indian Ministry of Health publications up to December 2025. Specific data on heart attack statistics were sourced from national crime and healthcare records. Pharmacology and mechanistic evidence were drawn from vaccine platforms and scientific reviews.

3. RESULT

3.1. COVID-19 Vaccines Used in India and Their Safety Profiles

3.1.1. Covishield (ChAdOx1 / AZD1222)

Covishield, manufactured by Serum Institute of India under license from AstraZeneca / Oxford, is an adenoviral (chimpanzee adenovirus) vector vaccine encoding the SARS-CoV-2 spike protein. It was one of the earliest vaccines in the Indian rollout.Globally, the AstraZeneca vaccine was linked to rare cases of thrombosis with thrombocytopenia syndrome (TTS / VITT), particularly following the first dose, with cerebral venous sinus thrombosis (CVST) and splanchnic vein thromboses being relatively more frequent. Regulatory agencies such as EMA and others issued warnings about possible risks (e.g., ~4–6 cases per million).In May 2024, AstraZeneca publicly admitted in a UK court that its COVID-19 vaccine had the potential to cause clotting events.^[1]An Indian Express article cites a 2022 Lancet Global Health study which found rates of TTS of 8.1 per million for first dose, 2.3 per million for second dose for the AstraZeneca vaccine globally.^[2]Indian reports suggest that in India the incidence of TTS with Covishield is extremely low, possibly much lower than in Western populations. A government official quoted that the TTS incidence is about 0.000003% (i.e. ~3 per 100 million) in India for Covishield.^[3]A study from Kerala (Kozhikode) analyzing severe adverse reactions of Covishield between Jan 16, 2021 and May 17, 2022, covering ~1.91 billion doses, reported 3,023 adverse reaction reports, of which 1,527 were classified as severe, and 592 deaths. Of those, only 11 deaths (2%) were judged to be consistently associated with the vaccine; about 270 serious AEs (~18%) were vaccine-product related; the rest were deemed coincidental. The authors also asserted that the apparent vaccine-induced thrombocytopenia rate in India (4 per 10 million) is far lower than in Western reports.^[4]Thus, Covishield has a known albeit very rare risk of clotting phenomena, with a more favorable risk profile in Indian data as reported to date.

3.1.2. Covaxin (BBV152)

Covaxin is a whole-virus inactivated vaccine developed in India. Its safety data in large populations has been generally favorable, with few reports of severe adverse events.In the “Serious adverse event following immunization and thromboembolic events associated with COVID-19 vaccination” analysis from India, 120 out of 1,112 serious AEFI reports were from Covaxin recipients (10.8%). Thromboembolic events were included among the serious AEs, though the causality assessment did not show consistent association with particular vaccines.^[5]Compared to adenoviral vector vaccines, inactivated vaccines are less often implicated in potent immune-mediated platelet activation, though one cannot fully exclude rare idiosyncratic events.

3.1.3. Other Vaccines (Less used)

Other vaccines such as mRNA (Pfizer, Moderna) and protein subunit ones were less used or not authorized widely in India (especially during early periods). Hence, most Indian safety data relate to Covishield and Covaxin.

3.2. Mechanistic and Pharmacologic Considerations: Could Vaccines Trigger Coronary Thrombosis?

To evaluate whether vaccination could meaningfully contribute to heart attacks, one must consider plausible biological mechanisms, risk magnitudes, and modifying factors.

3.2.1. Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT / TTS)

The best-described mechanism linking vaccination to thrombosis is VITT (also called TTS). This syndrome resembles heparin-induced thrombocytopenia (HIT) in that patients develop antibodies against platelet factor 4 (PF4), which activate platelets and trigger thrombosis in conjunction with low platelet counts. The key features:

Anti-PF4 autoantibodies: After vaccination (especially adenovirus vector vaccines), some individuals develop antibodies that bind PF4 and form immune complexes, which then activate platelets via FcγRIIa receptors, triggering thrombosis.

1. Platelet consumption / thrombocytopenia: Because platelets are used in clot formation, platelet counts drop.
2. Endothelial activation: The immune complexes, inflammation, and complement activation can injure endothelium and promote a prothrombotic milieu.
3. Hypercoagulable state Combined with local triggers, this may lead to thrombosis in unusual locations (cerebral, splanchnic veins) or in arteries.While VITT is primarily associated with unusual venous thromboses, arterial thrombosis including myocardial infarction has been described in rare reports globally.However, for vaccine-associated coronary thrombosis (causing AMI), several additional hurdles must be crossed:

• The arterial circulation in the coronary tree is under high shear stress and generally more “protected” from de novo clot formation than venous systems.
• Atherosclerotic plaque rupture and platelet aggregation often underlie typical AMI; vaccine-triggered thrombosis would have to act alongside or superimpose on underlying atherosclerotic disease.
• The window for VITT is usually within 5–30 days post vaccination; beyond that the biological plausibility is weaker.

Thus, mechanistically, vaccine-induced thrombosis triggering coronary events is plausible but likely extremely rare, and more likely in individuals with underlying susceptibility (subclinical plaque disease, prothrombotic predisposition).

3.2.2. Other Proposed Mechanisms

Beyond classical VITT, other mechanistic ideas have been proposed:

1. Immune/inflammatory activation: Vaccines trigger innate immune responses and systemic inflammation that could transiently increase coagulability (e.g. via increased fibrinogen, tissue factor expression, platelet reactivity). In individuals at risk, this might tip the balance.
2. Endothelial perturbation: Spike protein expression (or mRNA / vector components) might have off-target endothelial effects, though data are limited.
3. Molecular mimicry / autoimmune effects: Cross-reactive antibodies or complement activation might provoke vascular injury.
4. Vaccine adjuvant / excipient effects: Though in Covaxin and Covishield, adjuvants are not known to be strongly prothrombotic, rare idiosyncratic responses cannot be ruled out.
5. “Second hit” phenomena: A subclinical prothrombotic state (e.g. dehydration, infection, procoagulant comorbidity) coincident with vaccination might precipitate a clinical event.

Nevertheless, these mechanisms remain speculative; robust human mechanistic studies specifically linking vaccination to coronary thrombosis are lacking.

3.2.3. Dose / Time Dependence

In VITT, the first dose of adenoviral vector vaccines is more implicated; the second dose risk is much lower. Some systematic reviews suggest increased risk of thromboembolic events after the first dose of ChAdOx1-S but not consistent increase in arterial events such as AMI.^[6]

Time-wise, most clotting events appear in the first 4 to 28 days post-vaccination, with diminishing probability beyond that.

3.3. Clinical and Epidemiological Evidence: India and International

Below we summarize key studies addressing coronary thrombosis or AMI events temporally related to COVID-19 vaccination, focusing especially on Indian data.

3.3.1. Indian Evidence

3.3.1.1. Coronary Thrombo-embolic Events Study (Refai et al.)

A single-center observational Indian study (March–May 2021) enrolled 89 patients with angiographic evidence of coronary thrombus among acute coronary syndrome (ACS) admissions. Among these, 37 patients (42%) had a history of COVID-19 vaccination prior to the event. Timing from vaccination to event: <1 week in 9 (24%), 1–2 weeks in 4 (11%), 2–4 weeks in 15 (41%), >4 weeks in 9 (24%).In the vaccinated group, 28 (76%) had received Covishield, 9 (24%) Covaxin.There was no observed thrombocytopenia in vaccinated patients, and mortality rates (in-hospital and 30-day) were not significantly different between vaccinated vs non-vaccinated groups.^[7]

This is an intriguing observation but does not establish causation; vaccination prevalence in the general population and matching of risk factors were not fully addressed.

3.3.1.2. National Causality Analysis of Serious AEFIs (India)

In the Government of India’s publicly released causality assessment of 1,112 serious AEFI reports till March 29, 2022:

• 578 (52%) were judged “coincidental,” 218 (19.6%) “vaccine product–related,” and rest “indeterminate / inconsistent.”
• Among serious AEFI, 209 (18.8%) involved thromboembolic events. Among thromboembolic events, categories included:
• Acute coronary syndrome / myocardial infarction: 96 cases (45.9% of thromboembolic)
• Cerebrovascular accidents: 77 cases (36.8%)
• Myocardial infarction specifically: 54 cases (25.8%) among the thromboembolic subset
• The analysis did not find a consistent causal association between thromboembolic events and vaccine type (Covishield vs Covaxin).[1]

This suggests that while thrombotic events have been reported, they are a minority of serious AEFIs, and causal assignment remains weak.

3.3.1.3. Observational Study from Delhi — AMI Patients

A retrospective observational study was conducted among 1,578 patients admitted with acute myocardial infarction (AMI) at GB Pant Hospital, Delhi (August 2021 – August 2022). Among them, 1,086 (68.8%) were vaccinated (96% of those had two doses). Key findings:

• No specific clustering of AMI onset in any particular interval post-vaccination. ([www.ndtv.com][8])
• In fact, the vaccinated group had lower adjusted all-cause mortality at 30 days and six months compared to unvaccinated group. ([www.ndtv.com][8])
• Among STEMI cases, 185 (12%) occurred within 90–150 days post-vaccination; only 28 (2%) occurred within first 30 days.[9]

3.3.2. International / Other Evidence

• Several case reports and series from Europe, North America, and elsewhere document arterial thromboses (including myocardial infarction) following COVID-19 vaccination, sometimes in the context of VITT.
• Reviews of vaccine safety have often found a small but detectable increased risk of venous thromboembolism for some adenoviral vector vaccines, but risk of arterial events is less consistent.
• A systematic review cited in Indian press claimed that risk of venous cerebral or peripheral thrombosis is 2–3 times higher after first dose of ChAdOx1-S, but evidence for arterial events like AMI is low or very low.^[6]
• Regulatory bodies generally conclude that benefits of vaccination substantially outweigh rare vascular risks.

In sum, while rare case reports exist globally, strong epidemiological signal of post-vaccine heart attacks remains lacking.

3.4. Statistical and Incidence Considerations

3.4.1. Vaccine Dose Numbers and Adverse Event Reporting

• By April 2024, over 1.7 billion doses of Covishield were reported administered in India.^[10]
• In the earlier period (by November 2021), India had reported >49,819 adverse events following COVID vaccination; of these, 1,965 were serious.^[1]
• AEFI reporting is largely passive (via CoWIN, CMP) and subject to underreporting, especially of vascular events that may be attributed to background disease.

3.4.2. Background Incidence of Myocardial Infarction

To detect a vaccine-associated increase in heart attacks, one must compare with background rates of AMI in the population (adjusted for age, comorbidities). Because AMI is common in older adults with risk factors (hypertension, diabetes, dyslipidemia), random coincidence of vaccination and AMI is expected.

3.4.3. Excess Risk Estimation

Even an extremely small increased absolute risk (e.g. 1 per 100,000) is hard to detect against a background of many AMIs. Given the large denominator (hundreds of millions of vaccinations), only signal detection using pharmaco-vigilance, active surveillance, or self-controlled case series designs may reliably identify such small signals. No large-scale prospective study in India has clearly identified an excess AMI risk post-vaccination.

3.4.4. Time Clustering

If vaccination causes AMI, one might expect clustering of events in a narrow time window (e.g. within days to weeks) after vaccination. In the Delhi AMI study, only 2% of AMI cases occurred within first 30 days post-vaccination — not a strong clustering signal.^[9]In the Indian center coronary thrombus study, 24% had event <1 week, 41% between 2–4 weeks — raising possibility, but again without adjustment for expected rates (or matching) this remains hypothesis-generating.^[7]

4. DISCUSSION

4.1. Strengths and Limitations of Available Evidence

Strengths:

• Indian causality assessment of serious AEFIs provides a national-level overview.[5]
• The Delhi AMI study is relatively large (n = 1,578) and offers some statistical adjustment for mortality comparisons.[8]
• The coronary thrombus single center study provides angiographic data linking thrombus burden to vaccination status.[7]
• Case reports of VITT / TTS in India (e.g., CVST case) show that rare clotting syndromes are indeed possible.[11]

Limitations:

• Many studies are observational, retrospective, with limited control for confounding (age, comorbidities, baseline AMI risk).
• Passive surveillance AEFI systems are prone to underreporting, reporting bias, and inconsistent causality adjudication.
• Denominator data (i.e. how many people vaccinated, their risk profiles) is often lacking.
• Temporal associations do not imply causation.
• Many analyses treat all serious thrombotic events together; not all are coronary, and classification may be imprecise.
• Long-term risk beyond the immediate post-vaccine period is poorly studied.

4.2. Interpretation: Is There a Real Rise in Vaccine-Induced AMI?

Given the current data, a cautious interpretation is:

1. No convincing evidence for a substantial rise in heart attacks specifically attributable to vaccines in India thus far. The large Delhi AMI study did not find temporal clustering or higher mortality in vaccinated groups; on the contrary, vaccinated patients had somewhat better outcomes.
2. Thrombotic events do occur, but primarily in venous beds or cerebral/splanchnic circulation (i.e. VITT). Coronary thrombosis is less represented and may more often reflect coincidence than causation.
3. The mechanistic plausibility exists, but such events would likely be extremely rare and require susceptible individuals (pre-existing coronary disease, prothrombotic predisposition).
4. Because AMI is common in the population, distinguishing small excess risk from noise is challenging without active surveillance or controlled epidemiological designs.

4.3. Risk–Benefit Perspective

Even if a minuscule risk of coronary thrombosis exists, the benefits of vaccination—in preventing severe COVID-19, hospitalization, death, and associated cardiovascular complications—likely vastly outweigh such risks. Regulatory agencies globally have accepted this trade-off. Monitoring and early detection of rare events is preferable to vaccine withdrawal.

4.4. Recommendations and Future Directions

1. Active surveillance / pharmaco-epidemiological studies: Use self-controlled case series, cohort studies, or case–crossover designs to more robustly assess temporal risk of AMI post-vaccination.
2. Linkage to health data registries: Integrate vaccination records with cardiovascular event registries (e.g. hospital admissions for AMI) to monitor signal emergence.
3. Mechanistic studies: Investigate in vitro platelet activation, endothelial function assays, and PF4 antibody formation in vaccinated individuals, especially those with AMI.
4. Stratified risk assessment: Focus surveillance among higher-risk groups (older adults, coronary disease, thrombophilia) to see if any subgroup exhibits increased risk.
5. Transparent reporting and causality adjudication: Strengthen AEFI systems, encourage medical practitioners to report suspected cardiovascular AEs, and ensure robust causality assessment.
6. Public communication: Clarify that isolated reports do not necessarily imply causation, and that vaccination benefits remain predominant.

CONCLUSION

The question of a “rise in heart attack cases after COVID-19 vaccination in India” is important and understandable. However, based on currently available data, there is no clear and convincing evidence that COVID-19 vaccination (primarily Covishield and Covaxin) has led to a meaningful increase in acute myocardial infarction attributable to vaccine-induced coronary thrombosis. Rare thrombotic events, particularly VITT / TTS, are established (mainly in venous or cerebral circulations), and mechanistic plausibility exists, but the magnitude of any coronary risk is likely extremely small and difficult to detect against a common baseline of heart disease.Indian national AEFI surveillance data (1,112 serious AEFI reports) found thromboembolism in 18.8% of serious events, but did not find consistent causal links to vaccine type.^[5] A single-center coronary thrombus study observed higher thrombus burden among vaccinated versus non-vaccinated ACS patients, but without definitive causality.^[7] A larger AMI cohort from Delhi (n = 1,578) found no clustering of cases shortly after vaccination and lower adjusted mortality in vaccinated patients.^[8]Given that the absolute risks—if present—are extremely low, the overall benefit–risk balance strongly favors vaccination. Nonetheless, gaps in data, underreporting, and residual uncertainty warrant continued vigilance, prospective surveillance, and mechanistic inquiry. Future studies should emphasize active designs, linkage of cardiovascular event registries with vaccine databases, and subgroup analysis to ensure that even rare signals are not missed.

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