Flo: measuring the side effects of the COVID-19 vaccine on menstrual cycles

Flo, like other menstrual apps, facilitate observation and analysis of menstrual cycles and associated factors through the collection and interpretation of data entered by users. As a subgroup of health-related apps, menstrual apps form part of one of the most dynamic and rapidly growing developments in biomedicine and health care. Covid-19 has had an impact on the population’s health care. Due to the rapid initiation of vaccination programs around the world some concerns have been raised about the side effects associated with the vaccine. At a Covid vaccine appointment, people will probably be warned of possible side effects - fever, headache, a sore arm for a day or two afterwards. Changes to the menstrual cycle will not appear on this list. Women online around the world have started asking if early, heavy or painful periods might be an unlisted reaction to the jab. 

Schemes like the Yellow Card, run by the UK’s Medicines and Healthcare products Regulatory Agency (MHRA), are working to provide an early warning in regards to the safety of a prodIuct that may require further investigation. The scheme relies on voluntary reporting of suspected safety concerns or incidents by healthcare professionals and members of the public (patients, users, or carers). The Yellow Card has received reports from more than 20,000 women who suffered period problems after having their jab, including heavier than usual periods, delayed periods and unexpected vaginal bleeding. This is following approximately 41 million COVID-19 vaccine doses administered to women up to the 30th June 2021. The Yellow Card publishes weekly reports summarising the information received including other safety investigations carried out by the MHRA under the COVID-19 Vaccine Surveillance Strategy.

The Challenge

The purpose of the creation of a new post-covid-19 vaccine symptoms feature is to understand the menstrual experiences of people after they have been vaccinated for COVID-19. Benefits related to this research include being able to share people’s experiences and contribute to an often-overlooked area of health research.


- To focus on people’s experiences with their periods or other menstrual issues and associated symptoms after receiving at least one dose of the vaccine for COVID-19
- Determine the effects that are a common element of the vaccine response, and the bleeding patterns that can be an important way to understand how people’s immune systems are activated
- Identify user’s preferences and needs when using different menstrual cycle app features and ways that can be improved
- To focus on a specific and popular period tracker app to develop the research study requirements 
- To determine features integrations that can be accessed by users instantly
- To collect bleeding pattern data from users


Role: UX/UI Designer
Tools: Figma, Illustrator, Photoshop, Whimsical
Timeline: 3 weeks (July 2021)

Analysis & Research


We’ll determine people’s motivations when using health apps and, more specifically, menstrual cycle apps. We’ll work on finding pain points when accepting being part of a research study that involves monthly commitments.  


Secondary Research: Data assimilation from different sources, such Yellow Card scheme, Regenstrief Institute, Proyecto Eva and other online data from authentic sites.
Competitive Analysis: Examination of companies offering the same service or product and companies who offer similar, service and product but are serving a different need.
Survey: Questionnaire to gather information about the use of menstrual apps and Covid-19 vaccine side effects.

Secondary Research Findings

- Organisations around the world are working on gathering information from people experiencing unlisted Covid-19 vaccine side effects. The Yellow Card Scheme in the UK run by the MHRC publishes weekly reports summarising the information received by patients, users or carers in regards to the Covid-19 vaccine side effects. The Regenstrief Institute and Indiana University’s School of Medicine and Fairbanks School of Public Health partnered with REDCap and MSN News have developed and launched an international COVID-19 vaccine side effects survey for people who is been suffering changes in their menstrual cycle. The University of Granada (Spain) through the “Proyecto Eva” is currently investigating the effects of SARS COV-2 in women who are fertile. The initiative investigates possible menstrual alterations after the coronavirus vaccine. In the initial phase, information has been collected through more than five thousand surveys in which seven out of ten women claim to notice alterations.

- In 2014, health and fitness app usage grew at nearly twice the rate of overall app usage with women driving the trend as data by Flurry showed that 62% of heavy health app users (spending 3x the average on health and fitness apps) were female. Women’s health apps are therefore recognised as a huge opportunity and the tech industry is responding with a range of female-focused health apps.

- One of the biggest challenges to emerge from the growing number of health startups dealing with female reproduction is how they engage with marginalised groups typically left out of the design process.

- With the potential impact of COVID-19 on the femtech sector, there are some great investment opportunities. Entrepreneur can turnaround the scenario and come up with brilliant apps that can improve women’s health.

- With women comprising 50% of the global healthcare market and as primary caregivers for the elderly and children, there is a greater need for viable health solutions.

Competitive Analysis

Comparison of competitors’ strategy used to evaluate the strengths and weaknesses of period tracker apps and health apps as direct competitors and indirect competitors respectively. The analysis will help to develop an effective product strategy to create effective results.

User Survey

User surveys helped to identify what motivates people to use period tracker apps, to determine what type of features they are most interested in and to focus on an effective way of presenting a research study questionnaire and consequent results about the post-Covid-19 vaccine side effects.

Participants: 15
Adults between 21 and 46 years old
Locations: Spain, UK, Germany, USA

The questions were focused on two main points: 
- Their behaviour when using period tracker apps: how the user interacts with it, what features they used the most and which they didn’t find useful, how they received the information and what they would like to change about that. 
- Covid-19 vaccine details: whether they’ve been vaccinated or not, possible side effects after the first or second dose and their interest in participating in a research study about Covid-19 vaccine side effects.

All participants are period tracker app users, with Flo, Apple Health App and Period Tracker being the most popular. The majority of participants use these types of apps for keeping track of their menstrual cycle and to log in symptoms during the cycle.

The most popular features among the participants are, in order of popularity: the menstrual calendar, symptoms log, reminders and personalised reports.

 Participants mentioned they would like to add features to their app like:
- Recommendations based on symptoms
- Warnings when something seems to have changed or is suspicious 
- Assurance of data security Live chat with a specialist 
- Alerts to go to the doctor if needed 
- Timed alerts for when it’s needed (taking pills or shots)
- A way to access premium versions without paying by earning credits to unlock certain options

80% of participants have had the Covid-19 vaccine and 26.7% of them have experienced changes to their periods since. 60% of participants would be interested in joining a research study about the Covid-19 side effects and would be interested in receiving more information about the research results.

User Persona

The persona created has common goals and characteristics that represent the needs of a larger group of period tracker app users. The document includes behaviour patterns, goals, skills, attitudes, and background information, as well as the environment in which the persona operates.

Survey Findings

User's needs

- Most participants use the menstrual calendar, symptoms log, reminders and monthly reports in their apps
- Participants would like to add recommendations based on their symptoms to their apps
- Most participants need warnings when something seems to have changed or is deemed to be suspicious
- All participants need assurance of data security
- Some of them would like to have the option to chat with a specialist 
- Participants would appreciate having alerts to go to the doctor if needed
- Some participants would like to be able to personalise the alerts set up
- Some participants suggested the possibility of accessing premium through a credit system rather than paying
- All participants find graphic visualisation of data more enjoyable


- Most participants don’t like constant reminders to upgrade to premium 
- Some of them mentioned most apps overuse ‘pink colours’ 
- Some participants highlighted the importance of data protection when signing up 
- Some participants get frustrated with inaccurate data interpretation from their apps
- Participants find it unclear how to log symptom options (depending on the app)
- 66.7% of participants do not find push notifications useful 
- 81.8% of participants do not find monthly reports useful


- All participants find that the options given by the free versions of their app are enough to keep track of their menstrual cycle
- 46.2% of participants use other types of health apps
- 80% of participants have had the Covid-19 vaccine
- 26.7% of them have experienced changes to their periods since they had the vaccine
- 60% of participants would be interested in joining a research study about the Covid-19 side effects 
- 60% of participants would be interested in receiving information about their research results

Empathy map

The empathy map has been created to identify and understand the user persona’s situation and feelings, providing an overview of the user's experience. The document has helped synthesise the collective knowledge about users as a group, for better understanding of who they are.

Research Summary

- All participants have used period tracker apps before
- Most people get frustrated when accessing the logging symptoms option
- Most of them suggested new features to access information easily
- Some of them highlighted the importance of talking to specialists when needed
- None of them use the premium version of their apps
- Some of them would like to have access to reminders and alerts
- Some of them have had issues with their menstrual cycle after the Covid-19 vaccine
- Most of them would like to participate in a research study about the Covid-19 side effects

Design Research & Prototyping


The sitemap shows the different options the user will have once on the app homepage. They'll have the option of completing the questionnaire as well as access to the Covid-19 vaccine options. The user will find Covid-19 related information through the current app features.

User flow

The following flow shows the possible user's journey when accessing the app. The user will have the option to access the Covid-19 vaccine side effects questionnaire and access to the report, community, notifications and calendar through the current app features. The green diamond indicates the user's decisions (based on the survey); the blue square indicates the user's actions to access the options of the different pages (orange square).


A layout of the app  demonstrates what new interface elements will exist on key pages. The Covid-19 vaccine side effects questionnaire will allow the user to register their cycle patterns and possible health conditions. The new features added will allow the user to keep track of their menstrual cycle changes; to chat with an expert if needed, and to access Covid-19 vaccine-related information.

High Fidelity Prototype- First Draft

Covid-19 vaccine side effects questionnaire

The Covid-19 vaccine side effects questionnaire shown below has been based on a public survey by the Regenstrief Institute and Indiana University’s School of Medicine and Fairbanks School of Public Health partnered with REDCap and MSN News. The user will need to complete the questionnaire in order to be part of the research study.

Symptoms Chart & Stories

Flo's homepage shows a calendar and a chart displaying key information about the user's menstrual cycle. It also shows the log in symptom options as well as providing access to stories tailored to the user's needs. The new features added are shown within the symptoms charts: Covid-19 vaccine record system, bleeding pattern and hygiene products options. This information will be essential to the study research, the user will need to record their symptoms each day of their cycle.
Next to the log in symptoms option, Flo displays stories based on the users needs and preferences. We've added a Covid-19 section where the user can find information related to the research study, news and updates about the Covid-19 vaccine side effects.

Daily Research Questions Alerts

In order to collect valid information, the user needs to log in their bleeding patterns and the type of hygiene products used daily. The user will be notified through pushed notifications and will have access to the questions on homepage.

Covid-19 Community & Chats

Flo app has a Secret Chats option where users can anonymously discuss a variety of topics and get support from millions of other Flo users worldwide. We've added a Covid-19 section so users can have direct access to news, research study updates and FAQ about the Covid-19. We've added the chat with an expert feature in the news section as well as in the expert section inside the article.

The user will also have access to the chat through pop up windows in the FAQ section.

Covid-19 Research Study Reports

We've added a Covid-19 Vaccine Research option within the Graphs & Report section. The user will have access to a Comparison Report, where they can compare symptoms pre and post the Covid-19 vaccine. Through the Research Data option, users will be able to gain access to other organisations study reports working on the same matter.

Usability Testing

Usability Testing Planning

Test Objectives

- Observation of first impressions of the new features added, feelings and recognition
- Test the ease of use for the Covid-19 vaccine side effects questionnaire, log symptoms options, access to covid-19 related stories, symptoms alerts, access to Covid-19 secret chats, access to Covid-19 vaccine side effects research reports and data
-  Identify pain points when completing tasks
-  Determine how users complete the tasks

Test Methodolody

- High fidelity prototype of Covid-19 vaccine side effects features on the Flo App.


- Three to five potential participants who had already used period tracker apps (preferably Flo) aged between 14 and 48.


- Complete the Covid-19 side effects research study questionnaire
- Log in symptoms from the home page and through the alerts
- Access to the Covid-19 vaccine stories
- Access to the Covid-19 secret chat
- Access to the research study report

Test Goals

- Determine if the user found the process intuitive and clear
- Analyse pain points when finding key options 

Usability Testing Findings

The three participants highlighted the importance of being part of a real research study about the Covid-19 vaccine side effects. They agreed that the app, once knowing how it works, was easy to navigate. They are all period track app users and would consider using their app in a similar case. One out of three participants would have appreciated easier access to the chat option. One out of three considered alerts very useful as she highlighted she would need reminders to keep logging her symptoms. One out of three participants suggested the Covid-19 secret chat section should resemble the actual feature of the app. All participants were comfortable following the tasks and would like to join a real research study about the matter. 

Priority Revisions

Covid-19 Community

Changes made in the Secret Chats Covid-19 UI based on some feedback and iterations over the project.

News Section

A new tab layout has been added to the secret chats section in order to keep consistency in the new features implementation. News, research study and FAQ sections have been reorganised to correspond with the original design.

Research Study Section

The user will have access to more information about the Covid-19 vaccine side effects through the Research Study option within the Covid-19 section.

FAQ Section

The user will be able to access the FAQ through the Covid-19 section inside the secret chats. The user will be prompted with a pop-up window so they can chat with an expert if needed.

Chat Section

The user will be able to chat with an expert through the Covid-19 articles, inside the expert option and through the FAQ section.

View Final Prototype

Next Steps & Conclusion

Flo’s covid-19 vaccine side effects feature integrates essential options that will help researchers to gather information related to bleeding patterns and other symptoms in people who menstruate. In the future, the feature should be updated to include a research results option, a share option to connect with other schemes and to test the volunteers experience to determine possible improvements.

Understanding the menstrual experiences of people who menstruate after they've been vaccinated for Covid-19 through the integration of a new feature in Flo's app, has shown me that a considerable amount of people around the world are experiencing unusual symptoms. Thanks to the number of people who took part in the survey I could gather essential data about how they manage their health and their interest in taking part in a research study voluntary. This project aligns with my personal concerns about the unlisted side effects and being part of a research study from the University of Granada myself I'd find it very useful to have access to a similar integration on a period tracker app. The challenge of incorporating different features through the current app UI has been interesting as I had to incorporate new content not just in one section. I was pleased to see how the usability testing results showed the users found the journey intuitive and natural. Being in charge of designing the Covid-19 vaccine section has helped to gain more understanding of the procedures universities and institutions take in order to address the population's health concerns.

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